Submission #65439749

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Source Code Expand

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define xx first
#define yy second
#define PB push_back
#define MP make_pair

using namespace std;

using ll = long long;
using pii = pair<int,int>;
using tii = tuple<int,int,int>;
using vi = vector<int>;
using vvi = vector<vector<int>>;
template <typename T> using V = vector<T>;

template<class T> using uset = unordered_set<T>;
template<class T1, class T2> using umap = unordered_map<T1, T2>;

const vector<pair<int, int>> DIRS = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
constexpr int MOD = 1000000007;
mt19937_64 rnd(time(0));

template <class T>
using ordered_set =  __gnu_pbds::tree<T,__gnu_pbds::null_type,less<T>,__gnu_pbds::rb_tree_tag,__gnu_pbds::tree_order_statistics_node_update>;

void dfs(int cur, auto& adjList, auto& vis) {
    if ( vis[cur] ) return;
    vis[cur] = true;
    for ( int adj: adjList[cur] ) {
        dfs(adj, adjList, vis);
    }
}

signed main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int n, m;
    cin >> n >> m;
    vvi adjList(n);
    int u, v;
    for ( int i=0; i<m; i++ ) {
        cin >> u >> v;
        u--; v--;
        adjList[u].push_back(v);
        adjList[v].push_back(u);
    }
    if ( m != n ) {
        cout << "No\n";
        return 0;
    }
    for ( int i=0; i<n; i++ ) {
        if ( adjList[i].size() != 2 ) {
            cout << "No\n";
            return 0;
        }
    }
    vector<bool> vis(n, false);
    dfs(0, adjList, vis);
    for ( int i=0; i<n; i++ ) {
        if ( !vis[i] ) {
            cout << "No\n";
            return 0;
        }
    }
    cout << "Yes\n";
	return 0;
}

Submission Info

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