Add priority queue
John Schmidt
Andrew Kelley
parent
6fd2816431
commit
0eed72d687
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@ -609,6 +609,7 @@ set(ZIG_STD_FILES
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"os/windows/util.zig"
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"os/zen.zig"
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"pdb.zig"
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"priority_queue.zig"
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"rand/index.zig"
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"rand/ziggurat.zig"
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"segmented_list.zig"
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@ -9,6 +9,7 @@ pub const DynLib = @import("dynamic_library.zig").DynLib;
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pub const HashMap = @import("hash_map.zig").HashMap;
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pub const LinkedList = @import("linked_list.zig").LinkedList;
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pub const Mutex = @import("mutex.zig").Mutex;
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pub const PriorityQueue = @import("priority_queue.zig").PriorityQueue;
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pub const StaticallyInitializedMutex = @import("statically_initialized_mutex.zig").StaticallyInitializedMutex;
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pub const SegmentedList = @import("segmented_list.zig").SegmentedList;
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pub const SpinLock = @import("spinlock.zig").SpinLock;
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@ -59,7 +60,7 @@ test "std" {
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_ = @import("statically_initialized_mutex.zig");
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_ = @import("segmented_list.zig");
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_ = @import("spinlock.zig");
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_ = @import("base64.zig");
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_ = @import("build.zig");
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_ = @import("c/index.zig");
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@ -85,6 +86,7 @@ test "std" {
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_ = @import("net.zig");
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_ = @import("os/index.zig");
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_ = @import("pdb.zig");
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_ = @import("priority_queue.zig");
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_ = @import("rand/index.zig");
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_ = @import("sort.zig");
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_ = @import("testing.zig");
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@ -0,0 +1,331 @@
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const std = @import("index.zig");
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const Allocator = std.mem.Allocator;
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const debug = std.debug;
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const expect = std.testing.expect;
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const expectEqual = std.testing.expectEqual;
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pub fn PriorityQueue(comptime T: type) 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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compareFn: fn (a: T, b: T) bool,
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pub fn init(allocator: *Allocator, compareFn: fn (a: T, b: T) bool) 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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.compareFn = compareFn,
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};
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}
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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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pub fn add(self: *Self, elem: T) !void {
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try ensureCapacity(self, self.len + 1);
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self.items[self.len] = elem;
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var child_index = self.len;
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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 (!self.compareFn(child, parent)) 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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self.len += 1;
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}
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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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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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pub fn remove(self: *Self) T {
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const first = self.items[0];
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const last = self.items[self.len - 1];
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self.items[0] = last;
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self.len -= 1;
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siftDown(self);
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return first;
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}
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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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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) void {
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var index: usize = 0;
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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 (self.compareFn(e, smallest)) {
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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 (self.compareFn(e, smallest)) {
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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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pub fn ensureCapacity(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(T, self.items, better_capacity);
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}
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pub fn resize(self: *Self, new_len: usize) !void {
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try self.ensureCapacity(new_len);
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self.len = new_len;
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}
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pub fn shrink(self: *Self, new_len: usize) void {
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assert(new_len <= self.len);
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self.len = new_len;
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}
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const Iterator = struct {
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queue: *PriorityQueue(T),
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count: usize,
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fn next(it: *Iterator) ?T {
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if (it.count > it.queue.len - 1) 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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fn reset(it: *Iterator) void {
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it.count = 0;
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}
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};
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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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warn("{{ ");
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warn("items: ");
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for (self.items) |e, i| {
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if (i >= self.len) break;
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warn("{}, ", e);
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}
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warn("array: ");
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for (self.items) |e, i| {
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warn("{}, ", e);
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}
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warn("len: {} ", self.len);
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warn("capacity: {}", self.capacity());
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warn(" }}\n");
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}
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};
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}
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fn lessThan(a: u32, b: u32) bool {
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return a < b;
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}
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fn greaterThan(a: u32, b: u32) bool {
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return a > b;
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}
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const PQ = PriorityQueue(u32);
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test "std.PriorityQueue: add and remove min heap" {
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var queue = PQ.init(debug.global_allocator, lessThan);
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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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expectEqual(u32(7), queue.remove());
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expectEqual(u32(12), queue.remove());
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expectEqual(u32(13), queue.remove());
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expectEqual(u32(23), queue.remove());
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expectEqual(u32(25), queue.remove());
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expectEqual(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 = PQ.init(debug.global_allocator, lessThan);
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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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expectEqual(u32(1), queue.remove());
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expectEqual(u32(1), queue.remove());
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expectEqual(u32(1), queue.remove());
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expectEqual(u32(1), queue.remove());
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expectEqual(u32(2), queue.remove());
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expectEqual(u32(2), queue.remove());
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}
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test "std.PriorityQueue: removeOrNull on empty" {
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var queue = PQ.init(debug.global_allocator, lessThan);
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defer queue.deinit();
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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 = PQ.init(debug.global_allocator, lessThan);
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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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expectEqual(u32(2), queue.remove());
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expectEqual(u32(3), queue.remove());
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expectEqual(u32(9), queue.remove());
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}
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test "std.PriorityQueue: peek" {
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var queue = PQ.init(debug.global_allocator, lessThan);
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defer queue.deinit();
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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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expectEqual(u32(2), queue.peek().?);
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expectEqual(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 = PQ.init(debug.global_allocator, lessThan);
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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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expectEqual(u32(1), queue.remove());
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expectEqual(u32(2), queue.remove());
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expectEqual(u32(5), queue.remove());
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expectEqual(u32(6), queue.remove());
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expectEqual(u32(7), queue.remove());
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expectEqual(u32(7), queue.remove());
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expectEqual(u32(11), queue.remove());
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expectEqual(u32(12), queue.remove());
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expectEqual(u32(13), queue.remove());
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expectEqual(u32(14), queue.remove());
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expectEqual(u32(15), queue.remove());
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expectEqual(u32(15), queue.remove());
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expectEqual(u32(16), queue.remove());
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expectEqual(u32(21), queue.remove());
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expectEqual(u32(22), queue.remove());
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expectEqual(u32(24), queue.remove());
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expectEqual(u32(24), queue.remove());
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expectEqual(u32(25), queue.remove());
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}
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test "std.PriorityQueue: add and remove max heap" {
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var queue = PQ.init(debug.global_allocator, greaterThan);
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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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expectEqual(u32(54), queue.remove());
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expectEqual(u32(25), queue.remove());
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expectEqual(u32(23), queue.remove());
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expectEqual(u32(13), queue.remove());
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expectEqual(u32(12), queue.remove());
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expectEqual(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 = PQ.init(debug.global_allocator, greaterThan);
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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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expectEqual(u32(2), queue.remove());
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expectEqual(u32(2), queue.remove());
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expectEqual(u32(1), queue.remove());
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expectEqual(u32(1), queue.remove());
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expectEqual(u32(1), queue.remove());
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expectEqual(u32(1), queue.remove());
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}
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test "std.PriorityQueue: iterator" {
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var queue = PQ.init(debug.global_allocator, lessThan);
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var map = std.AutoHashMap(u32, void).init(debug.global_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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expectEqual(usize(0), map.count());
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}
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