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std.priority_queue: allow comparator to take a context parameter

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Arnavion 2021-12-15 17:46:04 -08:00
parent 877a1f2a29
commit 82e8930656
1 changed files with 69 additions and 37 deletions
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106
lib/std/priority_queue.zig
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@ -8,26 +8,28 @@ const expectEqual = testing.expectEqual;
const expectError = testing.expectError;
/// Priority queue for storing generic data. Initialize with `init`.
/// Provide `compareFn` that returns `Order.lt` when its first
/// argument should get popped before its second argument,
/// Provide `compareFn` that returns `Order.lt` when its second
/// argument should get popped before its third argument,
/// `Order.eq` if the arguments are of equal priority, or `Order.gt`
/// if the second argument should be popped first.
/// if the third argument should be popped first.
/// For example, to make `pop` return the smallest number, provide
/// `fn lessThan(a: T, b: T) Order { return std.math.order(a, b); }`
pub fn PriorityQueue(comptime T: type, comptime compareFn: fn (a: T, b: T) Order) type {
/// `fn lessThan(context: void, a: T, b: T) Order { _ = context; return std.math.order(a, b); }`
pub fn PriorityQueue(comptime T: type, comptime Context: type, comptime compareFn: fn (context: Context, a: T, b: T) Order) type {
return struct {
const Self = @This();
items: []T,
len: usize,
allocator: Allocator,
context: Context,
/// Initialize and return a priority queue.
pub fn init(allocator: Allocator) Self {
pub fn init(allocator: Allocator, context: Context) Self {
return Self{
.items = &[_]T{},
.len = 0,
.allocator = allocator,
.context = context,
};
}
@ -55,7 +57,7 @@ pub fn PriorityQueue(comptime T: type, comptime compareFn: fn (a: T, b: T) Order
const child = self.items[child_index];
const parent = self.items[parent_index];
if (compareFn(child, parent) != .lt) break;
if (compareFn(self.context, child, parent) != .lt) break;
self.items[parent_index] = child;
self.items[child_index] = parent;
@ -127,14 +129,14 @@ pub fn PriorityQueue(comptime T: type, comptime compareFn: fn (a: T, b: T) Order
var smallest = self.items[index];
if (left) |e| {
if (compareFn(e, smallest) == .lt) {
if (compareFn(self.context, e, smallest) == .lt) {
smallest_index = left_index;
smallest = e;
}
}
if (right) |e| {
if (compareFn(e, smallest) == .lt) {
if (compareFn(self.context, e, smallest) == .lt) {
smallest_index = right_index;
smallest = e;
}
@ -153,11 +155,12 @@ pub fn PriorityQueue(comptime T: type, comptime compareFn: fn (a: T, b: T) Order
/// PriorityQueue takes ownership of the passed in slice. The slice must have been
/// allocated with `allocator`.
/// Deinitialize with `deinit`.
pub fn fromOwnedSlice(allocator: Allocator, items: []T) Self {
pub fn fromOwnedSlice(allocator: Allocator, items: []T, context: Context) Self {
var queue = Self{
.items = items,
.len = items.len,
.allocator = allocator,
.context = context,
};
if (queue.len <= 1) return queue;
@ -207,7 +210,7 @@ pub fn PriorityQueue(comptime T: type, comptime compareFn: fn (a: T, b: T) Order
var update_index: usize = std.mem.indexOfScalar(T, self.items[0..self.len], elem) orelse return error.ElementNotFound;
const old_elem: T = self.items[update_index];
self.items[update_index] = new_elem;
switch (compareFn(new_elem, old_elem)) {
switch (compareFn(self.context, new_elem, old_elem)) {
.lt => siftUp(self, update_index),
.gt => siftDown(self, update_index),
.eq => {}, // Nothing to do as the items have equal priority
@ -215,7 +218,7 @@ pub fn PriorityQueue(comptime T: type, comptime compareFn: fn (a: T, b: T) Order
}
pub const Iterator = struct {
queue: *PriorityQueue(T, compareFn),
queue: *PriorityQueue(T, Context, compareFn),
count: usize,
pub fn next(it: *Iterator) ?T {
@ -258,19 +261,20 @@ pub fn PriorityQueue(comptime T: type, comptime compareFn: fn (a: T, b: T) Order
};
}
fn lessThan(a: u32, b: u32) Order {
fn lessThan(context: void, a: u32, b: u32) Order {
_ = context;
return std.math.order(a, b);
}
fn greaterThan(a: u32, b: u32) Order {
return lessThan(a, b).invert();
fn greaterThan(context: void, a: u32, b: u32) Order {
return lessThan(context, a, b).invert();
}
const PQlt = PriorityQueue(u32, lessThan);
const PQgt = PriorityQueue(u32, greaterThan);
const PQlt = PriorityQueue(u32, void, lessThan);
const PQgt = PriorityQueue(u32, void, greaterThan);
test "std.PriorityQueue: add and remove min heap" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
defer queue.deinit();
try queue.add(54);
@ -288,7 +292,7 @@ test "std.PriorityQueue: add and remove min heap" {
}
test "std.PriorityQueue: add and remove same min heap" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
defer queue.deinit();
try queue.add(1);
@ -306,14 +310,14 @@ test "std.PriorityQueue: add and remove same min heap" {
}
test "std.PriorityQueue: removeOrNull on empty" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
defer queue.deinit();
try expect(queue.removeOrNull() == null);
}
test "std.PriorityQueue: edge case 3 elements" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
defer queue.deinit();
try queue.add(9);
@ -325,7 +329,7 @@ test "std.PriorityQueue: edge case 3 elements" {
}
test "std.PriorityQueue: peek" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
defer queue.deinit();
try expect(queue.peek() == null);
@ -337,7 +341,7 @@ test "std.PriorityQueue: peek" {
}
test "std.PriorityQueue: sift up with odd indices" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
defer queue.deinit();
const items = [_]u32{ 15, 7, 21, 14, 13, 22, 12, 6, 7, 25, 5, 24, 11, 16, 15, 24, 2, 1 };
for (items) |e| {
@ -351,7 +355,7 @@ test "std.PriorityQueue: sift up with odd indices" {
}
test "std.PriorityQueue: addSlice" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
defer queue.deinit();
const items = [_]u32{ 15, 7, 21, 14, 13, 22, 12, 6, 7, 25, 5, 24, 11, 16, 15, 24, 2, 1 };
try queue.addSlice(items[0..]);
@ -365,7 +369,7 @@ test "std.PriorityQueue: addSlice" {
test "std.PriorityQueue: fromOwnedSlice trivial case 0" {
const items = [0]u32{};
const queue_items = try testing.allocator.dupe(u32, &items);
var queue = PQlt.fromOwnedSlice(testing.allocator, queue_items[0..]);
var queue = PQlt.fromOwnedSlice(testing.allocator, queue_items[0..], {});
defer queue.deinit();
try expectEqual(@as(usize, 0), queue.len);
try expect(queue.removeOrNull() == null);
@ -374,7 +378,7 @@ test "std.PriorityQueue: fromOwnedSlice trivial case 0" {
test "std.PriorityQueue: fromOwnedSlice trivial case 1" {
const items = [1]u32{1};
const queue_items = try testing.allocator.dupe(u32, &items);
var queue = PQlt.fromOwnedSlice(testing.allocator, queue_items[0..]);
var queue = PQlt.fromOwnedSlice(testing.allocator, queue_items[0..], {});
defer queue.deinit();
try expectEqual(@as(usize, 1), queue.len);
@ -385,7 +389,7 @@ test "std.PriorityQueue: fromOwnedSlice trivial case 1" {
test "std.PriorityQueue: fromOwnedSlice" {
const items = [_]u32{ 15, 7, 21, 14, 13, 22, 12, 6, 7, 25, 5, 24, 11, 16, 15, 24, 2, 1 };
const heap_items = try testing.allocator.dupe(u32, items[0..]);
var queue = PQlt.fromOwnedSlice(testing.allocator, heap_items[0..]);
var queue = PQlt.fromOwnedSlice(testing.allocator, heap_items[0..], {});
defer queue.deinit();
const sorted_items = [_]u32{ 1, 2, 5, 6, 7, 7, 11, 12, 13, 14, 15, 15, 16, 21, 22, 24, 24, 25 };
@ -395,7 +399,7 @@ test "std.PriorityQueue: fromOwnedSlice" {
}
test "std.PriorityQueue: add and remove max heap" {
var queue = PQgt.init(testing.allocator);
var queue = PQgt.init(testing.allocator, {});
defer queue.deinit();
try queue.add(54);
@ -413,7 +417,7 @@ test "std.PriorityQueue: add and remove max heap" {
}
test "std.PriorityQueue: add and remove same max heap" {
var queue = PQgt.init(testing.allocator);
var queue = PQgt.init(testing.allocator, {});
defer queue.deinit();
try queue.add(1);
@ -431,7 +435,7 @@ test "std.PriorityQueue: add and remove same max heap" {
}
test "std.PriorityQueue: iterator" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
var map = std.AutoHashMap(u32, void).init(testing.allocator);
defer {
queue.deinit();
@ -453,7 +457,7 @@ test "std.PriorityQueue: iterator" {
}
test "std.PriorityQueue: remove at index" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
defer queue.deinit();
try queue.add(3);
@ -476,7 +480,7 @@ test "std.PriorityQueue: remove at index" {
}
test "std.PriorityQueue: iterator while empty" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
defer queue.deinit();
var it = queue.iterator();
@ -485,7 +489,7 @@ test "std.PriorityQueue: iterator while empty" {
}
test "std.PriorityQueue: shrinkAndFree" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
defer queue.deinit();
try queue.ensureTotalCapacity(4);
@ -508,7 +512,7 @@ test "std.PriorityQueue: shrinkAndFree" {
}
test "std.PriorityQueue: update min heap" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
defer queue.deinit();
try queue.add(55);
@ -523,7 +527,7 @@ test "std.PriorityQueue: update min heap" {
}
test "std.PriorityQueue: update same min heap" {
var queue = PQlt.init(testing.allocator);
var queue = PQlt.init(testing.allocator, {});
defer queue.deinit();
try queue.add(1);
@ -539,7 +543,7 @@ test "std.PriorityQueue: update same min heap" {
}
test "std.PriorityQueue: update max heap" {
var queue = PQgt.init(testing.allocator);
var queue = PQgt.init(testing.allocator, {});
defer queue.deinit();
try queue.add(55);
@ -554,7 +558,7 @@ test "std.PriorityQueue: update max heap" {
}
test "std.PriorityQueue: update same max heap" {
var queue = PQgt.init(testing.allocator);
var queue = PQgt.init(testing.allocator, {});
defer queue.deinit();
try queue.add(1);
@ -568,3 +572,31 @@ test "std.PriorityQueue: update same max heap" {
try expectEqual(@as(u32, 2), queue.remove());
try expectEqual(@as(u32, 1), 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());
}