07_程序员必须掌握的8大排序算法_并归排序

并归排序

基本思想

归并（Merge）排序法是将两个（或两个以上）有序表合并成一个新的有序表，即把待排序序列分为若干个子序列，每个子序列是有序的。然后再把有序子序列合并为整体有序序列。

实例

用Java实现

import java.util.Arrays;  public class mergingSort {  int a[]={49,38,65,97,76,13,27,49,78,34,12,64,5,4,62,99,98,54,56,17,18,23,34,15,35,25,53,51};      public  mergingSort(){          sort(a,0,a.length-1);          for(int i=0;i<a.length;i++){        System.out.println(a[i]);          }            }      public void sort(int[] data, int left, int right) {           if(left<right){              //找出中间索引              int center=(left+right)/2;              //对左边数组进行递归              sort(data,left,center);              //对右边数组进行递归              sort(data,center+1,right);              //合并              merge(data,left,center,right);                 }      }      public void merge(int[] data, int left, int center, int right) {          int [] tmpArr=new int[data.length];          int mid=center+1;          //third记录中间数组的索引          int third=left;          int tmp=left;          while(left<=center&&mid<=right){              //从两个数组中取出最小的放入中间数组              if(data[left]<=data[mid]){                  tmpArr[third++]=data[left++];              }else{                  tmpArr[third++]=data[mid++];              }          }          //剩余部分依次放入中间数组          while(mid<=right){              tmpArr[third++]=data[mid++];          }          while(left<=center){              tmpArr[third++]=data[left++];          }          //将中间数组中的内容复制回原数组          while(tmp<=right){              data[tmp]=tmpArr[tmp++];          }          System.out.println(Arrays.toString(data));      }   }