堆排序

Author: tianqing.liang

12-Heap/HeapSort.dart

@@ -0,0 +1,20 @@
+import 'MaxHeap.dart';
+
+/**
+ * 堆排序
+ */
+class HeapSort {
+
+  HeapSort() {
+
+  }
+  static sort<E extends Comparable<E>>(List data) {
+    MaxHeap<E> maxHeap = MaxHeap.withCapacity(10);
+    for (E e in data){
+      maxHeap.add(e);
+    }
+    for (int i = data.length - 1; i >= 0; i --)
+      data[i] = maxHeap.extractMax();
+  }
+
+}

12-Heap/MaxHeap.dart

@@ -62,16 +62,15 @@ class MaxHeap<E extends Comparable<E>>{
 
     // 取出堆中最大元素
     E extractMax(){
-
       E ret = findMax();
       _swap(0, data!.length - 1);
       data!.removeLast();
-      siftDown(0);
+      _siftDown(0);
 
       return ret;
     }
 
-    siftDown(int k){
+    _siftDown(int k){
       while(_leftChild(k) < data!.length){
         int j = _leftChild(k); // 在此轮循环中,data[k]和data[j]交换位置
         if( j + 1 < data!.length &&
@@ -85,6 +84,15 @@ class MaxHeap<E extends Comparable<E>>{
       }
     }
 
+    // 取出堆中的最大元素，并且替换成元素e
+    E replace(E e){
+
+      E ret = findMax();
+      data![0] =e;;
+      _siftDown(0);
+      return ret;
+    }
+
     _swap(int i, int j){
       if(i < 0 || i >= data!.length || j < 0 || j >= data!.length)
         throw new Exception("Index is illegal.");