SRM441-D1-250 PerfectPermutation

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

const int OO = 1e9;
const double EPS = 1e-9;

class PerfectPermutation {
public:
    vector<vector<int>> graph;
    bool visited[51];

    void dfs(int i) {
        for(int e : graph[i]) {
            if(!visited[e]) {
                visited[e] = 1;
                dfs(e);
            }
        }
    }

    int reorder(vector<int> P) {
        graph.resize(P.size());
        memset(visited,0,sizeof(visited));
        for(int i = 0; i < P.size(); i++) {
            graph[P[i]].push_back(P[P[i]]);
            graph[P[P[i]]].push_back(P[i]);
        }
        int ans = 0;
        for(int i = 0; i < P.size(); i++) {
            if(!visited[i]) {
                visited[i] = 1;
                ans++;
                dfs(i);
            }
        }
        return (ans == 1 ? 0:ans);
    }
};