全排列（next_permutation)

next_permutation函数既可用于非重排列也可用于重排列；

 #include <bits/stdc++.h>
 #define MAXN 200000+10
 #define ll long long
 using namespace std;

 int a[MAXN];

 int main(void)
 {
     int n;
     cin >> n;
     for(int i=; i<n; i++)
     cin >> a[i];
     sort(a, a+n);
     do
     {
         for(int i=; i<n; i++)
         cout << a[i] << " ";
         cout << endl;
     }while(next_permutation(a, a+n));
     return ;
 }