Solution - Birthday Party (VT HSPC 2014)

Debugging Help
#1

Birthday Party – Kattis, Kattis: Birthday Party – Kattis, Kattis
code:

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
#define inf LONG_LONG_MAX
#define vi vector<int>
#define all(v) (v.begin(),v.end())
#define loop(n) for(int i=0;i<n;i++)
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define out(x) for(auto it : x){ cout<<it<<' ';} cout<<endl;
#define yes cout<<"Yes"<<'\n'
#define no cout<<"No"<<'\n'
void setIO(string name = "") {  // name is nonempty for USACO file I/O
	ios_base::sync_with_stdio(0);
	cin.tie(0);  // see Fast Input & Output
	if (name.size()) {
		freopen((name + ".in").c_str(), "r", stdin);  // see Input & Output
		freopen((name + ".out").c_str(), "w", stdout);
	}
}

int M=1e9+7;
vector<vi>g;
vi vis;

void dfs(int ver){
    if(vis[ver]==1)return;
    vis[ver]=1;
    for(auto it:g[ver]){
        dfs(it);
    }
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    setIO();
    int x,y;
    cin>>x>>y;
    while (x!=0 && y!=0)
    {   
        g.clear();
        vis.clear();
        g.resize(x);
        vis.resize(x,0);

        loop(y){
            int a,b;
            cin>>a>>b;
            g[a].push_back(b);
            g[b].push_back(a);
        }
        // needs to have a connected component each having two edges
        // nice hack if connected component chk is missing
        int cnt=0;
        dfs(0);
        loop(x){
            if(g[i].size()<2){cnt++;}
            if(vis[i]==0){cnt++;}
        }
        out(vis);
        (cnt!=0)?yes:no;

        cin>>x>>y;
    }
    
    return 0;
}

Issue: got wrong ans, is checking graph is connected and each having at least two edges is sufficient for deciding yes, no.