bc7 Little Pony and Permutation

As a unicorn, the ability of using magic is the distinguishing feature among other kind of pony. Being familiar with composition and decomposition is the fundamental course for a young unicorn. Twilight Sparkle is interested in the decomposition of permutations. A permutation of a set S = {1, 2, ..., n} is a bijection from S to itself. In the great magician —— Cauchy's two-line notation, one lists the elements of set S in the first row, and then for each element, writes its image under the permutation below it in the second row. For instance, a permutation of set {1, 2, 3, 4, 5} σ can be written as:

σ=(1225344351)

Here σ(1) = 2, σ(2) = 5, σ(3) = 4, σ(4) = 3, and σ(5) = 1.
Twilight Sparkle is going to decompose the permutation into some disjoint cycles. For instance, the above permutation can be rewritten as:

(1225344351)=(125)(34)

Help Twilight Sparkle find the lexicographic smallest solution. (Only considering numbers).

题目就是要求i σ(i) σ(σ(i))....选过了就不能重选，遍历一遍就OK 了

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <climits>
#include <vector>
#include <queue>
#include <cstdlib>
#include <string>
#include <set>
#include<stack>
#include<cmath>
#include<cassert>
using namespace std;
const int N=100010;
int a[N],vis[N];
int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        for(int i=1;i<=n;i++)
            scanf("%d",&a[i]);
        memset(vis,0,sizeof(vis));
        int cnt=0;
        for(int i=1;i<=n;i++)
        {
            if(vis[i])
                continue;
            printf("(");
            int t=i;
            int first=1;
            while(!vis[t])
            {
                vis[t]=1;
                if(first) first=0;
                else printf(" ");
                printf("%d",t);
                t=a[t];
            }
            printf(")");
        }
        printf("\n");
    }
    return 0;
}