Problem p02678 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long int
using namespace __gnu_pbds;
typedef tree<pair<ll, pair<ll, ll>>, null_type, less<pair<ll, pair<ll, ll>>>,
             rb_tree_tag, tree_order_statistics_node_update>
    ordered_set;
#define me BOSS
#define bug() cout << "AIkahne aise" << endl
#define PI acos(-1)
/* Precode Start Here *\\
     Sieve
void sieve()
{
    for(ll i=3; i<=2000; i+=2)
    {
        for(ll j=i*i; j<=4000000; j+=i)
            A[j]=1;
    }
    v.push_back(2);
    for(ll i=3; i<=4000000; i+=2)
        if(A[i]==0)
            v.push_back(i);
}

     Power Function Modulo P

ll modPow(ll a, ll x, ll p) {
    //calculates a^x mod p in logarithmic time.
    long res = 1;
    while(x > 0) {
        if( x % 2 != 0) {
            res = (res * a) % p;
        }
        a = (a * a) % p;
        x /= 2;
    }
    return res;
}


   factorial

ll fact(ll n)
{
    ll ans=1;
    for(ll i=1;i<=n;i++)
    {
        ans=(ans*i)%mod;
    }
    return ans;
}
     Calculating nCr using Fermats law Theorem

ll modInverse(ll a, ll p) {
    //calculates the modular multiplicative of a mod m.
    //(assuming p is prime).
    return modPow(a, p-2, p);
}


ll modBinomial(ll n, ll k, ll p) {
// calculates C(n,k) mod p (assuming p is prime).

    ll numerator = 1; // n * (n-1) * ... * (n-k+1)
    for (ll i=0; i<k; i++) {
        numerator = (numerator * (n-i) ) % p;
    }

    ll denominator = 1; // k!
    for (ll i=1; i<=k; i++) {
        denominator = (denominator * i) % p;
    }

    // numerator / denominator mod p.
    return ( numerator* modInverse(denominator,p) ) % p;
}
     num of divisor and euler totient

ll phi[1000001],mark[1000001],divi[1000001];;
void divisorPhi(ll n)
{
    for(int i=1;i<=n;i++)
        phi[i]=i;
    for(int i=2;i<=n;i++)
    {
        if(!mark[i])
        {
            for(int j=i;j<=n;j+=i)
            {
                mark[j]=1;
                phi[j]*=(1-1/(double)i);
            }
        }
    }
    for(ll i=1;i<=n;i++)
    {
        for(ll j=i;j<=n;j+=i)
            divi[j]++;
    }
}
/* Precode Ends */
#define mod 1000000007
ll dis[5000001], par[5000001], vis[300001];
vector<ll> v[300001];
map<ll, ll> myMap;
set<ll> mySet;
vector<pair<ll, ll>> vp;
priority_queue<ll> pq;
queue<ll> q;
priority_queue<ll, vector<ll>, std::greater<ll>> first;
ll po(ll a, ll n) {
  ll ans = 1;
  for (int i = 1; i <= n; i++)
    ans *= a;
  return ans;
}

void bfs(int start) {
  vis[start] = 1;
  dis[start] = 0;
  q.push(start);
  while (!q.empty()) {
    ll u = q.front();
    q.pop();
    for (int i = 0; i < v[u].size(); i++) {
      ll p = v[u][i];
      if (vis[p] == 0) {
        vis[p] = 1;
        dis[p] = dis[u] + 1;
        par[p] = u;
        q.push(p);
      } else if (dis[p] > dis[u] + 1) {
        dis[p] = dis[u] + 1;
        par[p] = u;
        q.push(p);
      }
    }
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  ll n, m;
  cin >> n >> m;
  for (int i = 1; i <= m; i++) {
    ll a, b;
    cin >> a >> b;
    v[a].push_back(b);
    v[b].push_back(a);
  }
  bfs(1);
  for (int i = 2; i <= n; i++) {
    if (vis[i] == 0) {
      cout << "No" << endl;
      return 0;
    }
  }
  cout << "Yes" << endl;
  for (int i = 2; i <= n; i++) {
    cout << par[i] << endl;
  }
  return 0;
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long int
using namespace __gnu_pbds;
typedef tree<pair<ll, pair<ll, ll>>, null_type, less<pair<ll, pair<ll, ll>>>,
             rb_tree_tag, tree_order_statistics_node_update>
    ordered_set;
#define me BOSS
#define bug() cout << "AIkahne aise" << endl
#define PI acos(-1)
/* Precode Start Here *\\
     Sieve
void sieve()
{
    for(ll i=3; i<=2000; i+=2)
    {
        for(ll j=i*i; j<=4000000; j+=i)
            A[j]=1;
    }
    v.push_back(2);
    for(ll i=3; i<=4000000; i+=2)
        if(A[i]==0)
            v.push_back(i);
}

     Power Function Modulo P

ll modPow(ll a, ll x, ll p) {
    //calculates a^x mod p in logarithmic time.
    long res = 1;
    while(x > 0) {
        if( x % 2 != 0) {
            res = (res * a) % p;
        }
        a = (a * a) % p;
        x /= 2;
    }
    return res;
}


   factorial

ll fact(ll n)
{
    ll ans=1;
    for(ll i=1;i<=n;i++)
    {
        ans=(ans*i)%mod;
    }
    return ans;
}
     Calculating nCr using Fermats law Theorem

ll modInverse(ll a, ll p) {
    //calculates the modular multiplicative of a mod m.
    //(assuming p is prime).
    return modPow(a, p-2, p);
}


ll modBinomial(ll n, ll k, ll p) {
// calculates C(n,k) mod p (assuming p is prime).

    ll numerator = 1; // n * (n-1) * ... * (n-k+1)
    for (ll i=0; i<k; i++) {
        numerator = (numerator * (n-i) ) % p;
    }

    ll denominator = 1; // k!
    for (ll i=1; i<=k; i++) {
        denominator = (denominator * i) % p;
    }

    // numerator / denominator mod p.
    return ( numerator* modInverse(denominator,p) ) % p;
}
     num of divisor and euler totient

ll phi[1000001],mark[1000001],divi[1000001];;
void divisorPhi(ll n)
{
    for(int i=1;i<=n;i++)
        phi[i]=i;
    for(int i=2;i<=n;i++)
    {
        if(!mark[i])
        {
            for(int j=i;j<=n;j+=i)
            {
                mark[j]=1;
                phi[j]*=(1-1/(double)i);
            }
        }
    }
    for(ll i=1;i<=n;i++)
    {
        for(ll j=i;j<=n;j+=i)
            divi[j]++;
    }
}
/* Precode Ends */
#define mod 1000000007
ll dis[5000001], par[5000001], vis[300001];
vector<ll> v[300001];
map<ll, ll> myMap;
set<ll> mySet;
vector<pair<ll, ll>> vp;
priority_queue<ll> pq;
priority_queue<ll, vector<ll>, std::greater<ll>> first;
ll po(ll a, ll n) {
  ll ans = 1;
  for (int i = 1; i <= n; i++)
    ans *= a;
  return ans;
}

void dfs(int start) {
  vis[start] = 1;
  for (int i = 0; i < v[start].size(); i++) {
    ll u = v[start][i];
    if (vis[u] == 0) {
      dis[u] = dis[start] + 1;
      par[u] = start;
      dfs(u);
    } else if (dis[u] > dis[start] + 1) {
      dis[u] = dis[start] + 1;
      par[u] = start;
      dfs(u);
    }
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  ll n, m;
  cin >> n >> m;
  for (int i = 1; i <= m; i++) {
    ll a, b;
    cin >> a >> b;
    v[a].push_back(b);
    v[b].push_back(a);
  }
  dfs(1);
  for (int i = 2; i <= n; i++) {
    if (vis[i] == 0) {
      cout << "No" << endl;
      return 0;
    }
  }
  cout << "Yes" << endl;
  for (int i = 2; i <= n; i++) {
    cout << par[i] << endl;
  }
  return 0;
}