归并排序（半夜睡不着写写基本算法）

#include <bits/stdc++.h>

using namespace std;

void margearray(int a[], int s, int e)
{
    int tmp[e-s+1], k = 0, mid = (s+e)/2;
    int i = s, j = mid+1;
    int m = mid, n=e;
    while(i<= m && j <= n)
    {
        if(a[i] <= a[j])
            tmp[k++] = a[i++];
        else
            tmp[k++] = a[j++];
    }
    while(i<=m)
    {
        tmp[k++] = a[i++];
    }
    while(j <= n)
    {
        tmp[k++] = a[j++];
    }
    for(int t = 0; t < k; t++)
        a[s+t] = tmp[t];
}
void margesort(int a[], int s, int e)
{
    if(s < e)
    {
        int mid = (s+e)/2;
        margesort(a, s, mid);
        margesort(a, mid+1, e);
        margearray(a, s, e);
    }
}

int main()
{
    int n;
    while (cin >> n)
    {
        int a[100100];
        for(int i = 0; i < n; i++)
            cin >> a[i];
        margesort(a, 0, n-1);
        for(int i = 0; i < n; i++)
            cout << a[i] << " " ;
        cout << endl;
    }
}