From ed8b20da787edd3747cc85708a0b9dd2c2e256d1 Mon Sep 17 00:00:00 2001
From: gingerBill <bill@gingerbill.org>
Date: Wed, 29 Dec 2021 14:38:39 +0000
Subject: [PATCH] Add `core:container/priority_queue`

---
 .../priority_queue/priority_queue.odin        | 140 ++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 core/container/priority_queue/priority_queue.odin

diff --git a/core/container/priority_queue/priority_queue.odin b/core/container/priority_queue/priority_queue.odin
new file mode 100644
index 000000000..f53dced38
--- /dev/null
+++ b/core/container/priority_queue/priority_queue.odin
@@ -0,0 +1,140 @@
+package container_priority_queue
+
+import "core:builtin"
+
+Priority_Queue :: struct($T: typeid) {
+	data:     [dynamic]T,
+	len:      int,
+	priority: proc(item: T) -> int,
+}
+
+DEFAULT_CAPACITY :: 16
+
+init_none :: proc(q: ^$Q/Priority_Queue($T), f: proc(item: T) -> int, allocator := context.allocator) {
+	init_len(q, f, 0, allocator)
+}
+init_len :: proc(q: ^$Q/Priority_Queue($T), f: proc(item: T) -> int, len: int, allocator := context.allocator) {
+	init_len_cap(q, f, 0, DEFAULT_CAPACITY, allocator)
+}
+init_len_cap :: proc(q: ^$Q/Priority_Queue($T), f: proc(item: T) -> int, len: int, cap: int, allocator := context.allocator) {
+	if q.data.allocator.procedure == nil {
+		q.data.allocator = allocator
+	}
+	builtin.resize(&q.data, cap)
+	q.len = len
+	q.priority = f
+}
+
+init :: proc{init_none, init_len, init_len_cap}
+
+
+delete :: proc(q: $Q/Priority_Queue($T)) {
+	builtin.delete(q.data)
+}
+
+clear :: proc(q: ^$Q/Priority_Queue($T)) {
+	q.len = 0
+}
+
+len :: proc(q: $Q/Priority_Queue($T)) -> int {
+	return q.len
+}
+
+cap :: proc(q: $Q/Priority_Queue($T)) -> int {
+	return builtin.cap(q.data)
+}
+
+space :: proc(q: $Q/Priority_Queue($T)) -> int {
+	return builtin.len(q.data) - q.len
+}
+
+reserve :: proc(q: ^$Q/Priority_Queue($T), capacity: int) {
+	if capacity > q.len {
+		builtin.resize(&q.data, capacity)
+	}
+}
+
+resize :: proc(q: ^$Q/Priority_Queue($T), length: int) {
+	if length > q.len {
+		builtin.resize(&q.data, length)
+	}
+	q.len = length
+}
+
+_grow :: proc(q: ^$Q/Priority_Queue($T), min_capacity: int = 8) {
+	new_capacity := max(builtin.len(q.data)*2, min_capacity, 1)
+	builtin.resize(&q.data, new_capacity)
+}
+
+
+push :: proc(q: ^$Q/Priority_Queue($T), item: T) {
+	if builtin.len(q.data) - q.len == 0 {
+		_grow(q)
+	}
+
+	s := q.data[:]
+	s[q.len] = item
+
+	i := q.len
+	for i > 0 {
+		p := (i - 1) / 2
+		if q.priority(s[p]) <= q.priority(item) { 
+			break 
+		}
+		s[i] = s[p]
+		i = p
+	}
+
+	q.len += 1
+	if q.len > 0 { 
+		s[i] = item 
+	} 
+}
+
+pop :: proc(q: ^$Q/Priority_Queue($T), loc := #caller_location) -> T {
+	val, ok := pop_safe(q)
+	assert(condition=ok, loc=loc)
+	return val
+}
+
+
+pop_safe :: proc(q: ^$Q/Priority_Queue($T)) -> (T, bool) {
+	if q.len > 0 {
+		s := q.data[:]
+		min := s[0]
+		root := s[q.len-1]
+		q.len -= 1
+
+		i := 0
+		for i * 2 + 1 < q.len {
+			a := i * 2 + 1
+			b := i * 2 + 2
+			c := b < q.len && q.priority(s[b]) < q.priority(s[a]) ? b : a
+
+			if q.priority(s[c]) >= q.priority(root) {
+				break
+			}
+			s[i] = s[c]
+			i = c
+		}
+
+		if q.len > 0 {
+			s[i] = root
+		}
+		return min, true
+	}
+	return T{}, false
+}
+
+peek :: proc(q: ^$Q/Priority_Queue($T), loc := #caller_location) -> T {
+	assert(condition=q.len > 0, loc=loc)
+
+	return q.data[0]
+}
+
+peek_safe :: proc(q: ^$Q/Priority_Queue($T)) -> (T, bool) {
+	if q.len > 0 {
+		return q.data[0], true
+	}
+	return T{}, false
+}
\ No newline at end of file