归并排序

方法1

#include <stdio.h>  
#include <stdlib.h>  

void Merge(int array[], int start, int middle, int end)  
{  
    int i, j, k, n1, n2;  

    n1 = middle - start + 1;                
    n2 = end - middle;   

    int *L = (int *)malloc(n1 * sizeof(int));  
    int *R = (int *)malloc(n2 * sizeof(int));  

    for (i = 0, k = start; i < n1; i++, k++)  
    {  
        L[i] = array[k];//左端取值   
    }  

    for (i = 0, k = middle + 1; i < n2; i++, k++)  
    {  
        R[i] = array[k];//右端取值   
    }  

    for (k = start, i = 0, j = 0; i < n1 && j < n2; k++)  
    {  
        if (L[i] < R[j])  
        {  
            array[k] = L[i];  
            i++;  
        }  
        else  
        {  
            array[k] = R[j];  
            j++;  
        }  
    }//比较插入   

    if (i < n1)  
    {  
        for (j = i; j < n1; j++, k++)  
        {  
            array[k] = L[j];  
        }  
    }  

    if (j < n2)  
    {  
        for (i = j; i < n2; i++, k++)  
        {  
            array[k] = R[i];  
        }  
    }//合并过程   
}  

void MergeSort(int array[], int start, int end)  
{  
    int middle;  
    int i;  

    if (start < end)  
    {  
        middle = (start + end) / 2;  

        MergeSort(array, start, middle);  
        MergeSort(array, middle + 1, end);  
        Merge(array, start, middle, end);  
    }  
}  

int main()  
{  
    int i = 0;  
    int a[] = {49, 38, 65, 97, 76, 13, 27};  
    int length = sizeof(a) / sizeof(a[0]);  

    MergeSort(a, 0, length -1);  

    for (i = 0 ; i < length; i++)  
    {  
        printf("%d ", a[i]);  
    }  
    printf("\n");  

    return 0;  
}

方法2

#include <stdio.h>  
#include<stdlib.h>  
void merging(int a[],int begin,int mid,int end)  
{  
    int *tmp = (int *)malloc(sizeof(int)*(end - begin + 1));  
    int i,j,k;  
    i = begin;  
    j = mid + 1;  
    k = 0;  

    while(i <= mid && j <=end)  
    {  
        if(a[i] < a[j])  
            tmp[k++] = a[i++];  
        else  
            tmp[k++] = a[j++];  
    }  

    while(i <= mid)  
        tmp[k++] = a[i++];  
    while(j <= end)  
        tmp[k++] = a[j++];  

    for(i = 0;i < k;i++)  
    {  
        a[begin + i] = tmp[i];  
    }  
    free(tmp);  

}  
void merge_sort(int a[],int begin,int end)  
{  
    int mid;  
    if(a == NULL || begin >= end)  
        return;  
        mid = (begin + end) / 2;  
        merge_sort(a,begin,mid);  
        merge_sort(a,mid + 1,end);  
        merging(a,begin,mid,end);  

}  
int main()  
{  
    int i,length;  
    int a[10] = {0};  
    printf("enter 10 num...\n");  
    for(i = 0;i < 10;i++)  
    {  
        scanf("%d",&a[i]);  
    }  
    length = sizeof(a)/sizeof(int);  

    merge_sort(a,0,length - 1);  

    for(i = 0;i < length;i++)  
    {  
        printf("%d  ",a[i]);  
    }  
    return 0;  
}