ADD: 29_priority_queue

Author: lixingliang

go/29_priority_queue/heap.go

@@ -0,0 +1,22 @@
+package pqueue
+
+func adjustHeap(src []Node, start, end int) {
+if start >= end {
+return
+}
+
+// 只需要保证优先级最高的节点在 src[1] 的位置即可
+for i := end / 2; i >= start; i-- {
+high := i
+if src[high].priority < src[2*i].priority {
+high = 2 * i
+}
+if 2*i+1 <= end && src[high].priority < src[2*i+1].priority {
+high = 2*i + 1
+}
+if high == i {
+continue
+}
+src[high], src[i] = src[i], src[high]
+}
+}

go/29_priority_queue/heap_test.go

@@ -0,0 +1,14 @@
+package pqueue
+
+import (
+"testing"
+
+"github.com/stretchr/testify/assert"
+)
+
+func Test_AdjustHeap(t *testing.T) {
+list := []Node{Node{0, 0}, Node{1, 1}, Node{2, 2}, Node{3, 3}, Node{4, 1}, Node{6, 6}}
+
+adjustHeap(list, 1, len(list)-1)
+assert.Equal(t, 6, list[1].value)
+}

go/29_priority_queue/priority_queue.go

@@ -0,0 +1,62 @@
+package pqueue
+
+// Node 队列节点
+type Node struct {
+value int
+priority int
+}
+
+// PQueue priority queue
+type PQueue struct {
+heap []Node
+
+capacity int
+used int
+}
+
+// NewPriorityQueue new
+func NewPriorityQueue(capacity int) PQueue {
+return PQueue{
+heap: make([]Node, capacity+1, capacity+1),
+capacity: capacity,
+used: 0,
+}
+}
+
+// Push 入队
+func (q *PQueue) Push(node Node) {
+
+if q.used > q.capacity {
+// 队列已满
+return
+}
+q.used++
+q.heap[q.used] = node
+// 堆化可以放在 Pop 中
+// adjustHeap(q.heap, 1, q.used)
+}
+
+// Pop 出队列
+func (q *PQueue) Pop() Node {
+if q.used == 0 {
+return Node{-1, -1}
+}
+// 先堆化, 再取堆顶元素
+adjustHeap(q.heap, 1, q.used)
+node := q.heap[1]
+
+q.heap[1] = q.heap[q.used]
+q.used--
+
+return node
+}
+
+// Top 获取队列顶部元素
+func (q *PQueue) Top() Node {
+if q.used == 0 {
+return Node{-1, -1}
+}
+
+adjustHeap(q.heap, 1, q.used)
+return q.heap[1]
+}

go/29_priority_queue/priority_queue_test.go

@@ -0,0 +1,74 @@
+package pqueue
+
+import (
+"testing"
+
+"github.com/stretchr/testify/assert"
+)
+
+func Test_Push(t *testing.T) {
+queue := NewPriorityQueue(100)
+
+queue.Push(Node{0, 1})
+assert.Equal(t, 0, queue.Top().value)
+
+queue.Push(Node{3, 1})
+assert.Equal(t, 0, queue.Top().value)
+
+queue.Push(Node{3, 2})
+assert.Equal(t, 3, queue.Top().value)
+
+queue.Push(Node{6, 6})
+assert.Equal(t, 6, queue.Top().value)
+
+queue.Push(Node{12, 5})
+assert.Equal(t, 6, queue.Top().value)
+
+queue.Push(Node{13, 8})
+assert.Equal(t, 13, queue.Top().value)
+}
+
+func Test_PushPop(t *testing.T) {
+queue := NewPriorityQueue(100)
+
+queue.Push(Node{0, 1})
+queue.Push(Node{3, 1})
+queue.Push(Node{3, 2})
+queue.Push(Node{6, 6})
+queue.Push(Node{12, 5})
+queue.Push(Node{13, 8})
+assert.Equal(t, 13, queue.Top().value)
+
+assert.Equal(t, 13, queue.Pop().value)
+assert.Equal(t, 6, queue.Pop().value)
+assert.Equal(t, 12, queue.Top().value)
+assert.Equal(t, 12, queue.Pop().value)
+
+queue.Push(Node{24, 8})
+assert.Equal(t, 24, queue.Top().value)
+}
+
+// 无法保证入队顺序和出队顺序的一致性
+// func Test_PushPop_Equal(t *testing.T) {
+//	queue := NewPriorityQueue(9)
+
+//	queue.Push(Node{0, 1}) // 8
+//	queue.Push(Node{3, 1}) // 9
+//	queue.Push(Node{3, 2}) // 3
+//	queue.Push(Node{6, 2}) // 4
+//	queue.Push(Node{11, 3}) // 2
+//	queue.Push(Node{12, 2}) // 5
+//	queue.Push(Node{13, 2}) // 6
+//	queue.Push(Node{19, 5}) // 1
+//	queue.Push(Node{17, 2}) // 7
+
+//	assert.Equal(t, 19, queue.Pop().value)
+//	assert.Equal(t, 11, queue.Pop().value)
+//	assert.Equal(t, 3, queue.Pop().value)
+//	assert.Equal(t, 6, queue.Pop().value)
+//	assert.Equal(t, 12, queue.Pop().value)
+//	assert.Equal(t, 13, queue.Pop().value)
+//	assert.Equal(t, 17, queue.Pop().value)
+//	assert.Equal(t, 0, queue.Pop().value)
+//	assert.Equal(t, 3, queue.Pop().value)
+// }

go/29_priority_queue/readme.md

@@ -0,0 +1,3 @@
+
+## TODO
+- 该实现方式不能保证 相同优先级的元素在出队列时 和入队列的顺序是一致的