归并排序

#include <iostream>
#include <stdio.h>
using namespace std;

const int N = 10e6 + 10;

int n;
int q[N],tmp[N];

void merge_sort(int q[], int l, int r)
{
    if (l >= r) return;

    int mid = (l + r)/ 2;//找到分界点

    merge_sort(q, l, mid);
    merge_sort(q, mid + 1, r);//对左右两段进行递归

    int k = 0;
    int i = l;
    int j = mid + 1;
    while (i <= mid && j <= r)
    {
        if (q[i] <= q[j]) tmp[k++] = q[i++];
        if (q[i] > q[j]) tmp[k++] = q[j++];    
    }//将较小的数赋给tmp
    while(i<=mid) tmp[k++] = q[i++];
    while(j<=r) tmp[k++] = q[j++];//若有一段用完，将另一段的剩余部分赋给tmp

    for (i = l,j = 0; i <= r; i++, j++)
    {
        q[i] = tmp[j];
    }//将tmp重新赋给原数组
}

int main()
{
    cin >> n;

    for (int i = 0; i < n; i++) cin >> q[i];

    merge_sort(q, 0, n-1);
        
    for (int i = 0; i < n; i++) printf("%d ", q[i]);
    return 0;
}