Submission #3454797

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> T;

int N, M;
vector<int> p(100001, 0);
vector<int> idx[101010];
int f[101010];

class UnionFind {
	public:
		vector<int> par, rank;
		void init(int n) {
			par = vector<int>(n);
			rank = vector<int>(n);
			for (int i = 0; i < n; i++) par[i] = i, rank[i] = 0;
		}
		// 木の根を求める
		int root(int x) {
			return (par[x] == x) ? x : par[x] = root(par[x]);
		}
		// xとyの属する集合を併合
		void unite(int x, int y) {
			x = root(x), y = root(y);
			if (x == y)return;
 
			if (rank[x] < rank[y]) par[x] = y;
			else {
				par[y] = x;
				if (rank[x] == rank[y]) rank[x]++;
			}
		}
		// xとyが同じ集合に属するか否か
		bool same(int x, int y) {
			return root(x) == root(y);
		}
};


int main(void){
    
    scanf("%d %d", &N, &M);
    for(int i = 1; i <= N; ++i) scanf("%d", &p[i]);
    
    UnionFind uf;
    uf.init(N + 1);
    
    for(int i = 0; i < M; ++i){
        int x, y; scanf("%d %d", &x, &y);
        uf.unite(x, y);
    }
    
    for(int i = 1; i <= N; ++i) idx[uf.root(i)].push_back(i);
    
    int ans = 0;
    for(int i = 1; i <= N; ++i){
        for(auto j : idx[i]) f[j] = 1;
        for(auto j : idx[i]) if(f[p[j]]) ++ans;
        for(auto j : idx[i]) f[j] = 0;
    }
    printf("%d\n", ans);
    
    return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:44:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &N, &M);
                           ^
./Main.cpp:45:51: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     for(int i = 1; i <= N; ++i) scanf("%d", &p[i]);
                                                   ^
./Main.cpp:51:41: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
         int x, y; scanf("%d %d", &x, &y);
                                         ^

Judge Result