Submission #27860144

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Source Code Expand

#include <bits/stdc++.h>
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define rep2(i,k,n) for (int i = (k); i < (n); ++i)
using namespace std;
using ll = long long;
using P = pair<int,int>;
// using P = pair<ll,ll>;

const ll INF = (ll)1e18;
// const int INF = (int)1e9+7;
template<typename T>
void chmin(T &a, T b) { a = min(a, b); }
template<typename T>
void chmax(T &a, T b) { a = max(a, b); }

struct UnionFind {
  vector<int> d;
  UnionFind(int n=0): d(n,-1) {}
  int find(int x) {
    if (d[x] < 0) return x;
    return d[x] = find(d[x]);
  }
  bool unite(int x, int y) {
    x = find(x); y = find(y);
    if (x == y) return false;
    if (d[x] > d[y]) swap(x,y);
    d[x] += d[y];
    d[y] = x;
    return true;
  }
  bool same(int x, int y) { return find(x) == find(y);}
  int size(int x) { return -d[find(x)];}
};

using Graph = vector<vector<int>>;

void solve() {
    int n, m;
    cin >> n >> m;

    UnionFind uf(n);
    Graph graph(n);
    rep(i,m) {
        int a, b;
        cin >> a >> b;
        a--, b--;
        if (uf.same(a,b)) {
            cout << "No" << endl;
            return;
        }
        uf.unite(a,b);
        graph[a].push_back(b);
        graph[b].push_back(a);
    }

    rep(i,n) {
        if (graph[i].size() > 2) {
            cout << "No" << endl;
            return;
        }
    }

    cout << "Yes" << endl;
}

int main() {
    solve();
    return 0;
}

Submission Info

Judge Result