From 018c337fa2cc5756963e068d9ffa95619e7746c7 Mon Sep 17 00:00:00 2001
From: nameczz <nameczz@126.com>
Date: Mon, 26 Nov 2018 23:38:43 +0800
Subject: [PATCH] add Javascript 28_heapsort

---
 javascript/28_heapsort/heap-sort.js | 65 +++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 javascript/28_heapsort/heap-sort.js

diff --git a/javascript/28_heapsort/heap-sort.js b/javascript/28_heapsort/heap-sort.js
new file mode 100644
index 00000000..572ddf06
--- /dev/null
+++ b/javascript/28_heapsort/heap-sort.js
@@ -0,0 +1,65 @@
+/**
+ * 堆排序
+ *
+ * Author: nameczz
+ */
+
+// 忽视数组的第一位
+class HeapSort {
+    constructor(originArray) {
+        this.originArray = originArray
+        console.log(this.originArray)
+    }
+    buildHeap() {
+        const arr = this.originArray
+        const startIndex = Math.floor(arr.length)
+        for (let i = startIndex; i >= 1; i--) {
+            this.heapify(arr, arr.length, i)
+        }
+        return arr
+    }
+
+    heapify(arr, len, i) {
+        while (true) {
+            let maxPos = i
+            // 如果index i拥有叶左节点 并且左节点较大
+            if (i * 2 <= len && arr[i] < arr[i * 2]) {
+                maxPos = i * 2
+            }
+            // 如果index i拥有叶右节点 与Max节点比较大小，选出父/左/右中最大的一个
+            if (i * 2 + 1 <= len && arr[maxPos] < arr[i * 2 + 1]) {
+                maxPos = i * 2 + 1
+            }
+            if (maxPos === i) break // 循环直到i节点为最大值
+            this.swap(arr, i, maxPos) // 交换位置, 父节点为父/左/右中最大的一个
+            i = maxPos // i为左/右节点，并尝试向下查找更大的值
+        }
+    }
+
+    sort() {
+        const arr = this.buildHeap() // 先建堆
+        let len = arr.length - 1
+        while (len > 1) {
+            this.swap(arr, 1, len) // 交换顶元素和最后一位。顶元素永远是最大的。
+            len--
+            this.heapify(arr, len, 1) //剩下的元素重新建堆 直到len === 1 停止
+        }
+        console.log(arr)
+    }
+
+    swap(arr, i, max) {
+        let temp = arr[i]
+        arr[i] = arr[max]
+        arr[max] = temp
+    }
+}
+
+const arr = [null]
+let i = 0
+while (i <= 10) {
+    const num = Math.floor(Math.random() * 100)
+    arr.push(num)
+    i++
+}
+const testHeap = new HeapSort(arr)
+testHeap.sort()
\ No newline at end of file