排序算法（JAVA实现）

package com.saigu;public class Main { public static void main(String[] args) {// TODO Auto-generated method stubtry{int a[] = {21,25,49,25,16,8};//quickSort(a,0,a.length - 1);//insertSort(a,0,a.length - 1);mergeSort(a,0,a.length - 1);for(int i = 0; i < a.length; i++)System.out.println(a[i]);}catch(Exception e){System.out.println(e);}}/**快速排序 * 时间复杂度O(nlogn),理想空间复杂度O(logn) * @param a:待排序数组 * @param left * @param right */public static void quickSort(int a[], int left, int right){if(left < right){//int pivotPos = changePos(a,left,right);//changePosint pivotPos = left;int pivot = a[left];for(int i = left + 1; i <= right; i++){if(a[i] < pivot){pivotPos++;int tmp = a[i];a[i] = a[pivotPos];a[pivotPos] = tmp;}}a[left] = a[pivotPos];a[pivotPos] = pivot;quickSort(a,left,pivotPos - 1);quickSort(a,pivotPos + 1,right);}}/**插入排序 * 时间复杂度O(n^2) * @param a * @param left * @param right */public static void insertSort(int a[], int left, int right){for(int i = left + 1; i <= right; i++){if(a[i] < a[i - 1]){int temp = a[i];int j = i - 1;do{a[j + 1] = a[j];j--;}while(j >= left && a[j] > temp);a[j + 1] = temp;}}}

<pre name="code" class="java">/**堆排序 *  * @param num * @param begin * @param end */public static void makeMaxHeap(int[] num, int begin, int end){int i = begin;int j = 2 * i + 1; //左节点int tmp = num[i];while(j <= end){if(j < end && num[j] < num[j + 1]) j++;//取左右节点中较大的一个if(tmp > num[j])break;else{num[i] = num[j];i = j;j = 2 * i + 1;}}num[i] = tmp;}public static void heapSort(int[] num){//构建最大堆for(int i = (num.length - 1 - 1)/2; i >= 0; i--){makeMaxHeap(num,i,num.length - 1);}//排序for(int i = num.length - 1; i >= 0; i--){int tmp = num[i];num[i] = num[0];num[0] = tmp;makeMaxHeap(num,0,i - 1);}}

<pre name="code" class="java">/**归并排序  * * 时间复杂度O(nlogn)  * * 稳定排序 * @param a  * * @param left  * * @param right */public static void mergeSort(int a[], int left, int right){int mid = (left + right)/2;if(left < right){mergeSort(a,left,mid);mergeSort(a,mid + 1,right);merge(a,left,mid,right);}}public static void merge(int a[], int left, int mid, int right){int[] tmp = new int[right - left + 1];int i = left;//左指针int j = mid + 1; //右指针int k = 0;//合并数组while(i <= mid && j <= right){if(a[i] < a[j])tmp[k++] = a[i++];elsetmp[k++] = a[j++];}//把左边剩余数组放进去while(i <= mid){tmp[k++] = a[i++];}//把右边剩余数组放进去while(j <= right){tmp[k++] = a[j++];}//赋值for(int p = 0; p < right - left + 1; p++)a[p + left] = tmp[p]; //注意这里是a[p + left];}