mirror of
https://github.com/ziglang/zig.git
synced 2024-11-30 09:02:32 +00:00
646 lines
21 KiB
Zig
646 lines
21 KiB
Zig
const std = @import("std.zig");
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const Allocator = std.mem.Allocator;
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const assert = std.debug.assert;
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const Order = std.math.Order;
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const testing = std.testing;
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const expect = testing.expect;
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const expectEqual = testing.expectEqual;
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const expectError = testing.expectError;
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/// Priority queue for storing generic data. Initialize with `init`.
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/// Provide `compareFn` that returns `Order.lt` when its second
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/// argument should get popped before its third argument,
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/// `Order.eq` if the arguments are of equal priority, or `Order.gt`
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/// if the third argument should be popped first.
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/// For example, to make `pop` return the smallest number, provide
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/// `fn lessThan(context: void, a: T, b: T) Order { _ = context; return std.math.order(a, b); }`
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pub fn PriorityQueue(comptime T: type, comptime Context: type, comptime compareFn: fn (context: Context, a: T, b: T) Order) type {
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return struct {
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const Self = @This();
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items: []T,
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len: usize,
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allocator: Allocator,
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context: Context,
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/// Initialize and return a priority queue.
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pub fn init(allocator: Allocator, context: Context) Self {
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return Self{
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.items = &[_]T{},
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.len = 0,
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.allocator = allocator,
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.context = context,
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};
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}
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/// Free memory used by the queue.
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pub fn deinit(self: Self) void {
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self.allocator.free(self.items);
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}
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/// Insert a new element, maintaining priority.
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pub fn add(self: *Self, elem: T) !void {
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try self.ensureUnusedCapacity(1);
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addUnchecked(self, elem);
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}
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fn addUnchecked(self: *Self, elem: T) void {
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self.items[self.len] = elem;
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siftUp(self, self.len);
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self.len += 1;
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}
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fn siftUp(self: *Self, start_index: usize) void {
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var child_index = start_index;
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while (child_index > 0) {
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var parent_index = ((child_index - 1) >> 1);
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const child = self.items[child_index];
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const parent = self.items[parent_index];
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if (compareFn(self.context, child, parent) != .lt) break;
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self.items[parent_index] = child;
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self.items[child_index] = parent;
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child_index = parent_index;
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}
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}
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/// Add each element in `items` to the queue.
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pub fn addSlice(self: *Self, items: []const T) !void {
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try self.ensureUnusedCapacity(items.len);
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for (items) |e| {
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self.addUnchecked(e);
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}
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}
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/// Look at the highest priority element in the queue. Returns
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/// `null` if empty.
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pub fn peek(self: *Self) ?T {
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return if (self.len > 0) self.items[0] else null;
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}
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/// Pop the highest priority element from the queue. Returns
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/// `null` if empty.
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pub fn removeOrNull(self: *Self) ?T {
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return if (self.len > 0) self.remove() else null;
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}
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/// Remove and return the highest priority element from the
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/// queue.
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pub fn remove(self: *Self) T {
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return self.removeIndex(0);
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}
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/// Remove and return element at index. Indices are in the
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/// same order as iterator, which is not necessarily priority
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/// order.
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pub fn removeIndex(self: *Self, index: usize) T {
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assert(self.len > index);
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const last = self.items[self.len - 1];
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const item = self.items[index];
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self.items[index] = last;
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self.len -= 1;
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if (index == 0) {
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siftDown(self, index);
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} else {
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const parent_index = ((index - 1) >> 1);
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const parent = self.items[parent_index];
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if (compareFn(self.context, last, parent) == .gt) {
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siftDown(self, index);
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} else {
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siftUp(self, index);
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}
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}
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return item;
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}
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/// Return the number of elements remaining in the priority
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/// queue.
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pub fn count(self: Self) usize {
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return self.len;
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}
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/// Return the number of elements that can be added to the
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/// queue before more memory is allocated.
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pub fn capacity(self: Self) usize {
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return self.items.len;
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}
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fn siftDown(self: *Self, start_index: usize) void {
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var index = start_index;
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const half = self.len >> 1;
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while (true) {
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var left_index = (index << 1) + 1;
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var right_index = left_index + 1;
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var left = if (left_index < self.len) self.items[left_index] else null;
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var right = if (right_index < self.len) self.items[right_index] else null;
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var smallest_index = index;
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var smallest = self.items[index];
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if (left) |e| {
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if (compareFn(self.context, e, smallest) == .lt) {
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smallest_index = left_index;
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smallest = e;
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}
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}
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if (right) |e| {
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if (compareFn(self.context, e, smallest) == .lt) {
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smallest_index = right_index;
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smallest = e;
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}
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}
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if (smallest_index == index) return;
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self.items[smallest_index] = self.items[index];
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self.items[index] = smallest;
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index = smallest_index;
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if (index >= half) return;
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}
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}
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/// PriorityQueue takes ownership of the passed in slice. The slice must have been
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/// allocated with `allocator`.
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/// Deinitialize with `deinit`.
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pub fn fromOwnedSlice(allocator: Allocator, items: []T, context: Context) Self {
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var queue = Self{
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.items = items,
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.len = items.len,
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.allocator = allocator,
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.context = context,
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};
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if (queue.len <= 1) return queue;
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const half = (queue.len >> 1) - 1;
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var i: usize = 0;
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while (i <= half) : (i += 1) {
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queue.siftDown(half - i);
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}
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return queue;
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}
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/// Ensure that the queue can fit at least `new_capacity` items.
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pub fn ensureTotalCapacity(self: *Self, new_capacity: usize) !void {
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var better_capacity = self.capacity();
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if (better_capacity >= new_capacity) return;
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while (true) {
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better_capacity += better_capacity / 2 + 8;
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if (better_capacity >= new_capacity) break;
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}
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self.items = try self.allocator.realloc(self.items, better_capacity);
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}
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/// Ensure that the queue can fit at least `additional_count` **more** item.
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pub fn ensureUnusedCapacity(self: *Self, additional_count: usize) !void {
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return self.ensureTotalCapacity(self.len + additional_count);
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}
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/// Reduce allocated capacity to `new_len`.
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pub fn shrinkAndFree(self: *Self, new_len: usize) void {
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assert(new_len <= self.items.len);
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// Cannot shrink to smaller than the current queue size without invalidating the heap property
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assert(new_len >= self.len);
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self.items = self.allocator.realloc(self.items[0..], new_len) catch |e| switch (e) {
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error.OutOfMemory => { // no problem, capacity is still correct then.
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self.items.len = new_len;
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return;
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},
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};
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}
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pub fn update(self: *Self, elem: T, new_elem: T) !void {
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const update_index = blk: {
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var idx: usize = 0;
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while (idx < self.len) : (idx += 1) {
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const item = self.items[idx];
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if (compareFn(self.context, item, elem) == .eq) break :blk idx;
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}
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return error.ElementNotFound;
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};
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const old_elem: T = self.items[update_index];
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self.items[update_index] = new_elem;
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switch (compareFn(self.context, new_elem, old_elem)) {
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.lt => siftUp(self, update_index),
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.gt => siftDown(self, update_index),
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.eq => {}, // Nothing to do as the items have equal priority
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}
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}
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pub const Iterator = struct {
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queue: *PriorityQueue(T, Context, compareFn),
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count: usize,
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pub fn next(it: *Iterator) ?T {
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if (it.count >= it.queue.len) return null;
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const out = it.count;
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it.count += 1;
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return it.queue.items[out];
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}
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pub fn reset(it: *Iterator) void {
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it.count = 0;
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}
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};
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/// Return an iterator that walks the queue without consuming
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/// it. Invalidated if the heap is modified.
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pub fn iterator(self: *Self) Iterator {
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return Iterator{
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.queue = self,
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.count = 0,
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};
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}
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fn dump(self: *Self) void {
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const print = std.debug.print;
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print("{{ ", .{});
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print("items: ", .{});
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for (self.items, 0..) |e, i| {
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if (i >= self.len) break;
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print("{}, ", .{e});
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}
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print("array: ", .{});
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for (self.items) |e| {
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print("{}, ", .{e});
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}
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print("len: {} ", .{self.len});
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print("capacity: {}", .{self.capacity()});
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print(" }}\n", .{});
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}
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};
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}
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fn lessThan(context: void, a: u32, b: u32) Order {
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_ = context;
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return std.math.order(a, b);
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}
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fn greaterThan(context: void, a: u32, b: u32) Order {
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return lessThan(context, a, b).invert();
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}
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const PQlt = PriorityQueue(u32, void, lessThan);
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const PQgt = PriorityQueue(u32, void, greaterThan);
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test "std.PriorityQueue: add and remove min heap" {
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var queue = PQlt.init(testing.allocator, {});
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defer queue.deinit();
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try queue.add(54);
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try queue.add(12);
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try queue.add(7);
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try queue.add(23);
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try queue.add(25);
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try queue.add(13);
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try expectEqual(@as(u32, 7), queue.remove());
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try expectEqual(@as(u32, 12), queue.remove());
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try expectEqual(@as(u32, 13), queue.remove());
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try expectEqual(@as(u32, 23), queue.remove());
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try expectEqual(@as(u32, 25), queue.remove());
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try expectEqual(@as(u32, 54), queue.remove());
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}
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test "std.PriorityQueue: add and remove same min heap" {
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var queue = PQlt.init(testing.allocator, {});
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defer queue.deinit();
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try queue.add(1);
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try queue.add(1);
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try queue.add(2);
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try queue.add(2);
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try queue.add(1);
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try queue.add(1);
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try expectEqual(@as(u32, 1), queue.remove());
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try expectEqual(@as(u32, 1), queue.remove());
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try expectEqual(@as(u32, 1), queue.remove());
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try expectEqual(@as(u32, 1), queue.remove());
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try expectEqual(@as(u32, 2), queue.remove());
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try expectEqual(@as(u32, 2), queue.remove());
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}
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test "std.PriorityQueue: removeOrNull on empty" {
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var queue = PQlt.init(testing.allocator, {});
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defer queue.deinit();
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try expect(queue.removeOrNull() == null);
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}
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test "std.PriorityQueue: edge case 3 elements" {
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var queue = PQlt.init(testing.allocator, {});
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defer queue.deinit();
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try queue.add(9);
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try queue.add(3);
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try queue.add(2);
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try expectEqual(@as(u32, 2), queue.remove());
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try expectEqual(@as(u32, 3), queue.remove());
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try expectEqual(@as(u32, 9), queue.remove());
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}
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test "std.PriorityQueue: peek" {
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var queue = PQlt.init(testing.allocator, {});
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defer queue.deinit();
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try expect(queue.peek() == null);
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try queue.add(9);
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try queue.add(3);
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try queue.add(2);
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try expectEqual(@as(u32, 2), queue.peek().?);
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try expectEqual(@as(u32, 2), queue.peek().?);
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}
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test "std.PriorityQueue: sift up with odd indices" {
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var queue = PQlt.init(testing.allocator, {});
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defer queue.deinit();
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const items = [_]u32{ 15, 7, 21, 14, 13, 22, 12, 6, 7, 25, 5, 24, 11, 16, 15, 24, 2, 1 };
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for (items) |e| {
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try queue.add(e);
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}
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const sorted_items = [_]u32{ 1, 2, 5, 6, 7, 7, 11, 12, 13, 14, 15, 15, 16, 21, 22, 24, 24, 25 };
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for (sorted_items) |e| {
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try expectEqual(e, queue.remove());
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}
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}
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test "std.PriorityQueue: addSlice" {
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var queue = PQlt.init(testing.allocator, {});
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defer queue.deinit();
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const items = [_]u32{ 15, 7, 21, 14, 13, 22, 12, 6, 7, 25, 5, 24, 11, 16, 15, 24, 2, 1 };
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try queue.addSlice(items[0..]);
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const sorted_items = [_]u32{ 1, 2, 5, 6, 7, 7, 11, 12, 13, 14, 15, 15, 16, 21, 22, 24, 24, 25 };
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for (sorted_items) |e| {
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try expectEqual(e, queue.remove());
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}
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}
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test "std.PriorityQueue: fromOwnedSlice trivial case 0" {
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const items = [0]u32{};
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const queue_items = try testing.allocator.dupe(u32, &items);
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var queue = PQlt.fromOwnedSlice(testing.allocator, queue_items[0..], {});
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defer queue.deinit();
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try expectEqual(@as(usize, 0), queue.len);
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try expect(queue.removeOrNull() == null);
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}
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test "std.PriorityQueue: fromOwnedSlice trivial case 1" {
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const items = [1]u32{1};
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const queue_items = try testing.allocator.dupe(u32, &items);
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var queue = PQlt.fromOwnedSlice(testing.allocator, queue_items[0..], {});
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defer queue.deinit();
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try expectEqual(@as(usize, 1), queue.len);
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try expectEqual(items[0], queue.remove());
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try expect(queue.removeOrNull() == null);
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}
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test "std.PriorityQueue: fromOwnedSlice" {
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const items = [_]u32{ 15, 7, 21, 14, 13, 22, 12, 6, 7, 25, 5, 24, 11, 16, 15, 24, 2, 1 };
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const heap_items = try testing.allocator.dupe(u32, items[0..]);
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var queue = PQlt.fromOwnedSlice(testing.allocator, heap_items[0..], {});
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defer queue.deinit();
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const sorted_items = [_]u32{ 1, 2, 5, 6, 7, 7, 11, 12, 13, 14, 15, 15, 16, 21, 22, 24, 24, 25 };
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for (sorted_items) |e| {
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try expectEqual(e, queue.remove());
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}
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}
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test "std.PriorityQueue: add and remove max heap" {
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var queue = PQgt.init(testing.allocator, {});
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defer queue.deinit();
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try queue.add(54);
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try queue.add(12);
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try queue.add(7);
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try queue.add(23);
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try queue.add(25);
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try queue.add(13);
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try expectEqual(@as(u32, 54), queue.remove());
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try expectEqual(@as(u32, 25), queue.remove());
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try expectEqual(@as(u32, 23), queue.remove());
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try expectEqual(@as(u32, 13), queue.remove());
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try expectEqual(@as(u32, 12), queue.remove());
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try expectEqual(@as(u32, 7), queue.remove());
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}
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test "std.PriorityQueue: add and remove same max heap" {
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var queue = PQgt.init(testing.allocator, {});
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defer queue.deinit();
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try queue.add(1);
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try queue.add(1);
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try queue.add(2);
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try queue.add(2);
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try queue.add(1);
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try queue.add(1);
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try expectEqual(@as(u32, 2), queue.remove());
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try expectEqual(@as(u32, 2), queue.remove());
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try expectEqual(@as(u32, 1), queue.remove());
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try expectEqual(@as(u32, 1), queue.remove());
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try expectEqual(@as(u32, 1), queue.remove());
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try expectEqual(@as(u32, 1), queue.remove());
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}
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test "std.PriorityQueue: iterator" {
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var queue = PQlt.init(testing.allocator, {});
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var map = std.AutoHashMap(u32, void).init(testing.allocator);
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defer {
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queue.deinit();
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map.deinit();
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}
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const items = [_]u32{ 54, 12, 7, 23, 25, 13 };
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for (items) |e| {
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_ = try queue.add(e);
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try map.put(e, {});
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}
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var it = queue.iterator();
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while (it.next()) |e| {
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_ = map.remove(e);
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}
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try expectEqual(@as(usize, 0), map.count());
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}
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test "std.PriorityQueue: remove at index" {
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var queue = PQlt.init(testing.allocator, {});
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defer queue.deinit();
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const items = [_]u32{ 2, 1, 8, 9, 3, 4, 5 };
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for (items) |e| {
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_ = try queue.add(e);
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}
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var it = queue.iterator();
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var idx: usize = 0;
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const two_idx = while (it.next()) |elem| {
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if (elem == 2)
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break idx;
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idx += 1;
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} else unreachable;
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var sorted_items = [_]u32{ 1, 3, 4, 5, 8, 9 };
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try expectEqual(queue.removeIndex(two_idx), 2);
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var i: usize = 0;
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while (queue.removeOrNull()) |n| : (i += 1) {
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try expectEqual(n, sorted_items[i]);
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}
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try expectEqual(queue.removeOrNull(), null);
|
|
}
|
|
|
|
test "std.PriorityQueue: iterator while empty" {
|
|
var queue = PQlt.init(testing.allocator, {});
|
|
defer queue.deinit();
|
|
|
|
var it = queue.iterator();
|
|
|
|
try expectEqual(it.next(), null);
|
|
}
|
|
|
|
test "std.PriorityQueue: shrinkAndFree" {
|
|
var queue = PQlt.init(testing.allocator, {});
|
|
defer queue.deinit();
|
|
|
|
try queue.ensureTotalCapacity(4);
|
|
try expect(queue.capacity() >= 4);
|
|
|
|
try queue.add(1);
|
|
try queue.add(2);
|
|
try queue.add(3);
|
|
try expect(queue.capacity() >= 4);
|
|
try expectEqual(@as(usize, 3), queue.len);
|
|
|
|
queue.shrinkAndFree(3);
|
|
try expectEqual(@as(usize, 3), queue.capacity());
|
|
try expectEqual(@as(usize, 3), queue.len);
|
|
|
|
try expectEqual(@as(u32, 1), queue.remove());
|
|
try expectEqual(@as(u32, 2), queue.remove());
|
|
try expectEqual(@as(u32, 3), queue.remove());
|
|
try expect(queue.removeOrNull() == null);
|
|
}
|
|
|
|
test "std.PriorityQueue: update min heap" {
|
|
var queue = PQlt.init(testing.allocator, {});
|
|
defer queue.deinit();
|
|
|
|
try queue.add(55);
|
|
try queue.add(44);
|
|
try queue.add(11);
|
|
try queue.update(55, 5);
|
|
try queue.update(44, 4);
|
|
try queue.update(11, 1);
|
|
try expectEqual(@as(u32, 1), queue.remove());
|
|
try expectEqual(@as(u32, 4), queue.remove());
|
|
try expectEqual(@as(u32, 5), queue.remove());
|
|
}
|
|
|
|
test "std.PriorityQueue: update same min heap" {
|
|
var queue = PQlt.init(testing.allocator, {});
|
|
defer queue.deinit();
|
|
|
|
try queue.add(1);
|
|
try queue.add(1);
|
|
try queue.add(2);
|
|
try queue.add(2);
|
|
try queue.update(1, 5);
|
|
try queue.update(2, 4);
|
|
try expectEqual(@as(u32, 1), queue.remove());
|
|
try expectEqual(@as(u32, 2), queue.remove());
|
|
try expectEqual(@as(u32, 4), queue.remove());
|
|
try expectEqual(@as(u32, 5), queue.remove());
|
|
}
|
|
|
|
test "std.PriorityQueue: update max heap" {
|
|
var queue = PQgt.init(testing.allocator, {});
|
|
defer queue.deinit();
|
|
|
|
try queue.add(55);
|
|
try queue.add(44);
|
|
try queue.add(11);
|
|
try queue.update(55, 5);
|
|
try queue.update(44, 1);
|
|
try queue.update(11, 4);
|
|
try expectEqual(@as(u32, 5), queue.remove());
|
|
try expectEqual(@as(u32, 4), queue.remove());
|
|
try expectEqual(@as(u32, 1), queue.remove());
|
|
}
|
|
|
|
test "std.PriorityQueue: update same max heap" {
|
|
var queue = PQgt.init(testing.allocator, {});
|
|
defer queue.deinit();
|
|
|
|
try queue.add(1);
|
|
try queue.add(1);
|
|
try queue.add(2);
|
|
try queue.add(2);
|
|
try queue.update(1, 5);
|
|
try queue.update(2, 4);
|
|
try expectEqual(@as(u32, 5), queue.remove());
|
|
try expectEqual(@as(u32, 4), queue.remove());
|
|
try expectEqual(@as(u32, 2), queue.remove());
|
|
try expectEqual(@as(u32, 1), queue.remove());
|
|
}
|
|
|
|
test "std.PriorityQueue: update after remove" {
|
|
var queue = PQlt.init(testing.allocator, {});
|
|
defer queue.deinit();
|
|
|
|
try queue.add(1);
|
|
try expectEqual(@as(u32, 1), queue.remove());
|
|
try expectError(error.ElementNotFound, queue.update(1, 1));
|
|
}
|
|
|
|
test "std.PriorityQueue: siftUp in remove" {
|
|
var queue = PQlt.init(testing.allocator, {});
|
|
defer queue.deinit();
|
|
|
|
try queue.addSlice(&.{ 0, 1, 100, 2, 3, 101, 102, 4, 5, 6, 7, 103, 104, 105, 106, 8 });
|
|
|
|
_ = queue.removeIndex(std.mem.indexOfScalar(u32, queue.items[0..queue.len], 102).?);
|
|
|
|
const sorted_items = [_]u32{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 100, 101, 103, 104, 105, 106 };
|
|
for (sorted_items) |e| {
|
|
try expectEqual(e, queue.remove());
|
|
}
|
|
}
|
|
|
|
fn contextLessThan(context: []const u32, a: usize, b: usize) Order {
|
|
return std.math.order(context[a], context[b]);
|
|
}
|
|
|
|
const CPQlt = PriorityQueue(usize, []const u32, contextLessThan);
|
|
|
|
test "std.PriorityQueue: add and remove min heap with contextful comparator" {
|
|
const context = [_]u32{ 5, 3, 4, 2, 2, 8, 0 };
|
|
|
|
var queue = CPQlt.init(testing.allocator, context[0..]);
|
|
defer queue.deinit();
|
|
|
|
try queue.add(0);
|
|
try queue.add(1);
|
|
try queue.add(2);
|
|
try queue.add(3);
|
|
try queue.add(4);
|
|
try queue.add(5);
|
|
try queue.add(6);
|
|
try expectEqual(@as(usize, 6), queue.remove());
|
|
try expectEqual(@as(usize, 4), queue.remove());
|
|
try expectEqual(@as(usize, 3), queue.remove());
|
|
try expectEqual(@as(usize, 1), queue.remove());
|
|
try expectEqual(@as(usize, 2), queue.remove());
|
|
try expectEqual(@as(usize, 0), queue.remove());
|
|
try expectEqual(@as(usize, 5), queue.remove());
|
|
}
|