update pq

content/posts/algorithm/data structure/优先队列.md

@@ -1,6 +1,7 @@
 ---
 title: '优先队列'
 date: 2022-09-23T14:43:36+08:00
+lastmod: 2024-04-25
 series: [data structure]
 categories: [algorithm]
 ---
@@ -9,66 +10,78 @@ JavaScript 中没有内置优先队列这个数据结构，需要自己来实现
 
 ```javascript
 class PriorityQueue {
-  constructor(data, comp) {
-    this.data = data
-    this.comp = comp
-    for (let i = data.length >> 1; i >= 0; --i) {
-      this.down(i)
+    constructor(data, cmp) {
+        this.data = data
+        this.cmp = cmp
+        for (let i = data.length >> 1; i >= 0; --i) {
+            this.down(i)
+        }
     }
-  }
-  down(i) {
-    let left = 2 * i + 1
-    while (left < this.size()) {
-      let min = left + 1 && this.comp(this.data[left + 1], this.data[left]) ? left + 1 : left // 细节，left+1 在前
-      min = this.comp(this.data[i], this.data[min]) ? i : min
-      if (min === i) {
-        break
-      }
-      this.swap(i, min)
-      i = min
-      left = 2 * i + 1
+    down(i) {
+        let left = 2 * i + 1
+        while (left < this.data.length) {
+            let temp
+            if (left + 1) {
+                temp = this.cmp(this.data[left + 1], this.data[i]) ? left + 1 : i
+            }
+            temp = this.cmp(this.data[temp], this.data[left]) ? temp : left
+            if (temp === i) {
+                break
+            }
+            this.swap(this.data, temp, i)
+            i = temp
+            left = 2 * i + 1
+        }
     }
-  }
-  up(i) {
-    while (i >= 0 && this.comp(this.data[(i - 1) >> 1], this.data[i])) {
-      this.swap((i - 1) >> 1, i)
-      i = (i - 1) >> 1
+    up(i) {
+        while (i >= 0) {
+            const parent = (i - 1) >> 1
+            if (this.cmp(this.data[i], this.data[parent])) {
+                this.swap(this.data, parent, i)
+                i = parent
+            } else {
+                break
+            }
+        }
+    }
+    push(val) {
+        this.up(this.data.push(val) - 1)
+    }
+    poll() {
+        this.swap(this.data, 0, this.data.length - 1)
+        const top = this.data.pop()
+        this.down(0)
+        return top
+    }
+
+    swap(data, i, j) {
+        const temp = data[i]
+        data[i] = data[j]
+        data[j] = temp
     }
-  }
-  push(val) {
-    this.up(this.data.push(val) - 1)
-  }
-  poll() {
-    this.swap(0, this.size() - 1)
-    const top = this.data.pop()
-    this.down(0)
-    return top
-  },
-  size() {
-    return this.data.length
-  }
-  swap(i, j) {
-    const temp = this.data[i]
-    this.data[i] = this.data[j]
-    this.data[j] = temp
-  }
 }
 ```
 
+<!--
+之前的版本 过于精炼，今天重新写个语义比较简单的
+自己重新写的时候，差点就写成递归版本了，请记住，迭代一版是要使用 while 的，通过 while 条件来控制循环
+第二点就是 比较器内，down i 在后，那么 up 里 i 就在前，一般互斥
+-->
+
 测试：
 
 ```js
 const pq = new PriorityQueue([4, 2, 3, 5, 6, 1, 7, 8, 9], (a, b) => a - b > 0)
 console.log('📌📌📌 ~ pq', pq)
-console.log(pq.pop())
-console.log(pq.pop())
-console.log(pq.pop())
-console.log(pq.pop())
-console.log(pq.pop())
-console.log(pq.pop())
-console.log(pq.pop())
-console.log(pq.pop())
-console.log(pq.pop())
+console.log(pq.poll())
+console.log(pq.poll())
+console.log(pq.poll())
+pq.push(10)
+pq.push(20)
+console.log(pq.poll())
+console.log(pq.poll())
+console.log(pq.poll())
+console.log(pq.poll())
 ```
 
 ---