归并排序

思路见排序思想

自己处理的时候开始和结束的边界问题总是处理不好，还需要多看几遍
代码：

#include <iostream>using namespace std;void merge(int *data,int start,int end,int *result);void merge_sort(int *data, int start, int end, int *result);void merge_sort(int *data, int start, int end, int *result){    if(1 == end - start)//如果区间中只有两个元素，则对这两个元素进行排序    {        if(data[start] > data[end])        {            int temp  = data[start];            data[start] = data[end];            data[end] = temp;        }        return;    }    else if(0 == end - start)//如果只有一个元素，则不用排序        return;    else    {        //继续划分子区间，分别对左右子区间进行排序        merge_sort(data,start,(end-start+1)/2+start,result);        merge_sort(data,(end-start+1)/2+start+1,end,result);        //开始归并已经排好序的start到end之间的数据        merge(data,start,end,result);        //把排序后的区间数据复制到原始数据中去        for(int i = start;i <= end;++i)            data[i] = result[i];    }}void merge(int *data,int start,int end,int *result){    int left_length = (end - start + 1) / 2 + 1;//左部分区间的数据元素的个数    int left_index = start;    int right_index = start + left_length;    int result_index = start;    while(left_index < start + left_length && right_index < end+1)    {        //对分别已经排好序的左区间和右区间进行合并        if(data[left_index] <= data[right_index])            result[result_index++] = data[left_index++];        else            result[result_index++] = data[right_index++];    }    while(left_index < start + left_length)        result[result_index++] = data[left_index++];    while(right_index < end+1)        result[result_index++] = data[right_index++];}int main(){    int data[] = {9,6,7,22,20,33,16,20};    const int length = 8;    int result[length];    cout << "Before sorted:" << endl;    for(int i = 0;i < length;++i)        cout << data[i] << "  ";    cout << endl;    cout << "After sorted:" << endl;    merge_sort(data,0,length-1,result);    for(int i = 0;i < length;++i)        cout << data[i] << "  ";    cout << endl;    system("pause");    return 0;}