归并排序（C语言版本）

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。

代码：

#include<stdio.h>#include<windows.h>void merge_array(int *arr,int low,int mid,int high){    int k,i;    int *temp = (int *)malloc((high-low+1)*sizeof(int));    int left_low = low;    int left_high = mid;    int right_low = mid + 1;    int right_high = high;    for(k=0;left_low<=left_high && right_low<=right_high;k++)    {        if(arr[left_low]<=arr[right_low])        {            temp[k] = arr[left_low++];        }else        {            temp[k] = arr[right_low++];        }    }    if(left_low<=left_high)    {        for(i=left_low;i<=left_high;i++)        {            temp[k++] = arr[i];        }    }    if(right_low<=right_high)    {        for(i=right_low;i<=right_high;i++)        {            temp[k++] = arr[i];        }    }    for(i=0;i<high-low+1;i++)    {        arr[low+i] = temp[i];    }    free(temp);    return;}void merge_sort(int *arr,int first,int last){    int mid = 0;    if(first<last)    {        mid = (first+last)/2;        merge_sort(arr,first,mid);        merge_sort(arr,mid+1,last);        merge_array(arr,first,mid,last);    }    return;}int main(){    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};    int n= 28;    int i;    for(i=0;i<n;i++)    {        printf("%d\t",a[i]);    }    printf("\n\n");    merge_sort(a,0,n-1);    for(i=0;i<n;i++)    {        printf("%d\t",a[i]);    }    printf("\n");    system("pause");    return 0;}