Submission #3417996

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Source Code Expand

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

struct UnionFind{
    vector<int> par;
    UnionFind(int N) : par(N){
        for(int i = 0; i < N; i++){
            par[i] = -1;
        }
    }
    int root(int x){
        if(par[x] < 0) return x;
        else return par[x] = root(par[x]);
    }
    void unite(int x, int y){
        int rx = root(x);
        int ry = root(y);
        if(rx == ry) return;
        else{
            if(par[rx] > par[ry]) swap(rx, ry);
            par[rx] += par[ry];
            par[ry] = rx;
       }
   }
    bool same(int x, int y){
        return root(x) == root(y);
    }
    void check(){
        for(auto x : par){
            cout << x << " ";
        }
        cout << endl;
    }
};

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    int N, M;
    cin >> N >> M;
    
    UnionFind UF(N);
    unordered_map<int, bool> mp;
    for(int i = 0; i < M; i++){
        int u, v;
        cin >> u >> v;
        u--;
        v--;
        if(UF.same(u, v)){
            mp[UF.root(u)] = true;
        }
        UF.unite(u, v);
    }

    int ans = 0;
    for(int i = 0; i < N; i++){
        if(UF.par[i] < 0){
            if(mp[UF.root(i)] == true);
            else ans++;
        }
    }

    cout << ans << endl;

    return 0;
}

Submission Info

Judge Result