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选择排序学过的有三种:简单选择排序、树形选择排序、堆排序
今天先来简单的了解一下堆排序:
完全二叉树,即从头到尾,从左到右依次排序,符合大堆(小堆)都行,即ki>=k2i && ki >= k2i+1
由于此处使用的是数组,则最长为array.length-1,并且 ki>=k2i+1 && ki >= k2i+2
下面的例子是百度上搜的,便于理解
实例如下:
public class MyHeap { public static void main(String[] args) { int[] array = {49,38,65,97,76,13,27,49 }; print(array); HeapSort(array); print(array); } public static int[] HeapSort(int[] array){ int n = (array.length-1)/2; for (int i = n; i >= 0; i--) { MaxHeap(array,i); } return array; } /**判断一个元素与其i*2+1(2)的关系*/ public static int[] MaxHeap(int[] array,Integer i){ int large = i; int index = 2*i+1; if(index< array.length && array[i]>array[index]){ large = index; } index = 2*i +2; if(index< array.length && array[i]>array[index]){ if( array[large]>array[index] ){ large = index; } } if(large != i){ int temp =array[i]; array[i] = array[large]; array[large] = temp; print(array);//每次交换顺序有打印 if(large <= array.length/2){ MaxHeap(array,large);//交换后,如果大的一层有下层,则再次判断大的一层是否符合 } } return array; } /**打印数组*/ public static void print(int[] array){ for (int i = 0; i < array.length; i++) { System.out.print(array[i] + " "); } System.out.println(); } }
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原文地址:http://www.cnblogs.com/blogofcookie/p/5845586.html