random_shuffle

#include<bits/stdc++.h>#define Ll long longusing namespace std;int main(){    scanf("%d",&n);    srand(time(0));    for(int i=1;i<=n;i++)a[i]=i;    while(++sum<=1000)           random_shuffle(a+1,a+n+1);}

这样可以让a数组重新随机排列一遍