八大排序算法之-堆排序 java代码

import java.util.Arrays;/** * Created by Administrator on 2017/8/2. */public class heapSort_select {    public static void main(String args[]) {        int[] arr = { 6, 9, 1, 3, 1, 2, 2, 5, 6, 1, 3, 5, 9, 7, 2, 5, 6, 1, 9 };        //[1, 1, 1, 1, 2, 2, 2, 3, 3, 5, 5, 5, 6, 6, 6, 7, 9, 9, 9]        heapSort(arr,0,arr.length-1);        System.out.println(Arrays.toString(arr));    }    /*算法思想：    * 大根堆：根部最大，可用于求最小k个数    * 小根堆：根部最小，可用于求最大k个数    *    * 1.首先将序列构建成大根堆    * 2.取出当前最大堆根节点，将其与序列末尾的元素进行交换；    * （此时，序列末尾的值已经是最大值）    * 3.对交换后的n-1个元素进行调整，使其满足大顶堆的性质    * 4.重复2,3直到堆中只有一个元素为止*/    /*时间复杂度：O(nlogn)    * 空间复杂度：*/    private static void heapSort(int[] arr, int start, int end) {        /*if (arr==null || arr.length<=1) {        }*/        for (int i = 0; i<=end; i++) {            heapInsert(arr,arr[i],i);        }        System.out.println(Arrays.toString(arr));        for (int i = end - 1; i>=0; i--) {            swap(arr,0,i+1);            selfBalanceHeap(arr,0,i);        }    }    private static void selfBalanceHeap(int[] heap, int index, int end) {        int left = index * 2 + 1;        int right = index * 2 + 2;        int largest = index;        while (left<=end) {            if ( heap[left]>heap[index]) {                largest = left;            }            if (right<=end && heap[right]>heap[largest]) {//此处应该和heap【largest】进行比较，即最大值，否则会出错                largest = right;            }            if (index!=largest) {                swap(heap,index,largest);            }else {                break;            }            index = largest;            left = index*2 +1;            right = index*2+2;        }    }    private static void heapInsert(int[] heap, int value, int index) {        heap[index] = value;        while (index!=0) {            int parent = (index - 1)/2;            if (heap[parent] <heap[index]) {                swap(heap,parent,index);                index = parent;            }else {                break;            }        }    }    private static void swap(int[] heap, int parent, int index) {        int tmp = heap[parent];        heap[parent] = heap[index];        heap[index] = tmp;    }}