DFS-全排列

 void dfs(int x)
 {
     if(x>n)
     {
         for(int i=;i<=n;++i) cout<<a[i];
         cout<<endl;
         return;
     }
     for(int i=;i<=n;++i)
     {
         if(!v[i])
         {
             a[x]=i;v[i]=;
             dfs(x+);
             v[i]=;
         }
     }
 }
 int main()
 {
     scanf("%d",&n);
     dfs();
     return ;
 }