归并排序（C语言实现）

#include <stdio.h>
#include <string.h>

#define LEN 20

int a[LEN];
int n;

void merge(int left, int mid, int right)
{
    
    
        int n1 = mid - left + 1;
        int n2 = right - mid;
        int l[n1], r[n2];
        int i, j, k;
        for (i = 0; i < n1; i++)
                l[i] = a[left+i];
        for (j = 0; j < n2; j++)
                r[j] = a[mid+1+j];
        i = j = 0;
        for (k = left; i < n1 && j < n2; ++k) {
    
    
                if (l[i] < r[j]) {
    
    
                        a[k] = l[i];
                        ++i;
                } else {
    
    
                        a[k] = r[j];
                        ++j;
                }
        }
        if (i < n1)
                for (; i < n1; i++) {
    
    
                        a[k] = l[i];
                        ++k;
                }
        if (j < n2)
                for (; j < n2; ++j) {
    
    
                        a[k] = r[j];
                        ++k;
                }
}

void sort(int left, int right)
{
    
    
        int mid;
        if (left < right) {
    
    
                mid = (left + right) / 2;
                sort(left, mid);
                sort(mid + 1, right);
                merge(left, mid, right);
        }
}

int main(void)
{
    
    
        memset(a, -1, sizeof(a));
        scanf("%d", &n);
        for (int i = 0; i < n; i++)
                scanf("%d", &a[i]);
        sort(0, n-1);
        for (int i = 0; i < n; i++)
                printf("%d ", a[i]);
        printf("\n");
        return 0;
}