Problem p02573 (C++) — buggy submission, verdict: Runtime Error

/*
Author : Aditya Gupta
Team : TechTurtle
Date : 29-08-2020
Time : 20:05:54
*/

#include <bits/stdc++.h>
#define ll long long int
#define ld long double
#define vll vector<ll>
#define vvll vector<vll>
#define vld vector<ld>
#define vvld vector<vld>
#define pll pair<ll, ll>
#define vpll vector<pll>
#define mp make_pair
#define pb push_back
#define MOD 1000000007
#define endl "\\n"
#define flash                                                                  \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(NULL);
#define test                                                                   \\
  ll t;                                                                        \\
  cin >> t;                                                                    \\
  while (t--)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define fst first
#define scd second
#define mk(arr, n, type) type *arr = new type[n];

#define forn(i, n) for (ll(i) = 0; (i) < (n); ++(i))
#define for1(i, n) for (ll(i) = 1; (i) <= (n); ++(i))
#define forr(i, n) for (ll(i) = (n)-1; (i) >= 0; --(i))
#define forab(i, a, b, c) for (ll(i) = a; (i) <= (b); (i) += (c))

using namespace std;

///////////////////////////////////////////////////////////////////////// Maths
/////////////////////////////////////////////////////////////////////////////////

// vll sieve;
// void Sieve(int N){  //smallest prime factor
//	const ll maxn = N;
//	sieve.resize(maxn);
//	forn(i,maxn) sieve[i] = i;
//	sieve[1] = -1;
//	sieve[0] = -1;
//	forab(i,2,maxn,1) if(i == sieve[i]) for(ll j = i*i ; j < maxn ; j+=i)
//if(sieve[j] == j) sieve[j] = i;
//
////	for(auto i:sieve){
////		cout<<i<<" ";
////	}
//
//}
vll sieve;
vll *Sieve(int N) {
  const ll maxn = N;
  sieve.resize(maxn);
  forn(i, maxn) sieve[i] = 1;
  sieve[1] = 0;
  sieve[0] = 0;
  forab(i, 2, maxn, 1) if (1 == sieve[i]) for (ll j = i * i; j < maxn; j += i)
      sieve[j] = 0;

  vll *primes = new vll();
  primes->pb(2);
  for (int i = 3; i < maxn; i += 2)
    if (sieve[i]) {
      primes->pb(i);
    }
  return primes;
}

ll extended_GCD(ll a, ll b, ll &x, ll &y) {
  if (a == 0) {
    x = 0;
    y = 1;
    return b;
  }
  ll x1, y1;
  ll gcd = extended_GCD(b % a, a, x1, y1);
  x = y1 - (b / a) * x1;
  y = x1;
  return gcd;
}

ll ncr(ll n, ll k) {
  ll r = 1;
  if (k > n - k)
    k = n - k;
  for (ll i = 0; i < k; i++) {
    r *= (n - i);
    r /= (i + 1);
  }
  return r;
}

ll power(ll a, ll b, ll m = MOD) {
  ll res = 1;
  while (b > 0) {
    if (b & 1)
      res = (res * a) % m;
    a = (a * a) % m;
    b >>= 1;
  }

  return res;
}

ll modinv(ll a, ll mod = MOD) {
  ll x, y;
  extended_GCD(a, mod, x, y);
  if (x < 0)
    x += mod;
  return x;
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
bool prime(int n) {
  int c = 0;
  for (int i = 2; (i * i) <= n; i++) {
    if (n % i == 0) {
      c++;
      return false;
    }
  }
  if (c == 0)
    return true;
}
// bool compareInterval(char i1, char i2)
//{
//    return (i1 < i2);
//}
// int countoperation(int n,m){
// 	vector<int> d<m+1,-1>;
// }
vector<int> v[200006];
int vis[200006];
int c;

void dfs(int n) {
  vis[n] = 1;
  c++;
  for (int i : v[n]) {
    if (!vis[i])
      dfs(i);
  }
}
void solve() {

  int n, e;
  cin >> n >> e;
  forn(i, e) {
    int a, b;
    cin >> a >> b;
    v[a].pb(b);
    v[b].pb(a);
  }
  int s = 0;

  for (int i = 1; i <= n; i++) {

    if (!vis[i]) {
      c = 0;
      dfs(i);
      s = max(s, c);
    }
  }

  cout << s << "\\n";
}

int main() {
  flash
  //	freopen("input.txt","r",stdin);
  //	freopen("output.txt","w",stdout);

  //	test
  solve();
  return 0;
}

Error: 0

Fixed submission:

/*
Author : Aditya Gupta
Team : TechTurtle
Date : 29-08-2020
Time : 20:05:54
*/

#include <bits/stdc++.h>
#define ll long long int
#define ld long double
#define vll vector<ll>
#define vvll vector<vll>
#define vld vector<ld>
#define vvld vector<vld>
#define pll pair<ll, ll>
#define vpll vector<pll>
#define mp make_pair
#define pb push_back
#define MOD 1000000007
#define endl "\\n"
#define flash                                                                  \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(NULL);
#define test                                                                   \\
  ll t;                                                                        \\
  cin >> t;                                                                    \\
  while (t--)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define fst first
#define scd second
#define mk(arr, n, type) type *arr = new type[n];

#define forn(i, n) for (ll(i) = 0; (i) < (n); ++(i))
#define for1(i, n) for (ll(i) = 1; (i) <= (n); ++(i))
#define forr(i, n) for (ll(i) = (n)-1; (i) >= 0; --(i))
#define forab(i, a, b, c) for (ll(i) = a; (i) <= (b); (i) += (c))

using namespace std;

///////////////////////////////////////////////////////////////////////// Maths
/////////////////////////////////////////////////////////////////////////////////

// vll sieve;
// void Sieve(int N){  //smallest prime factor
//	const ll maxn = N;
//	sieve.resize(maxn);
//	forn(i,maxn) sieve[i] = i;
//	sieve[1] = -1;
//	sieve[0] = -1;
//	forab(i,2,maxn,1) if(i == sieve[i]) for(ll j = i*i ; j < maxn ; j+=i)
//if(sieve[j] == j) sieve[j] = i;
//
////	for(auto i:sieve){
////		cout<<i<<" ";
////	}
//
//}
vll sieve;
vll *Sieve(int N) {
  const ll maxn = N;
  sieve.resize(maxn);
  forn(i, maxn) sieve[i] = 1;
  sieve[1] = 0;
  sieve[0] = 0;
  forab(i, 2, maxn, 1) if (1 == sieve[i]) for (ll j = i * i; j < maxn; j += i)
      sieve[j] = 0;

  vll *primes = new vll();
  primes->pb(2);
  for (int i = 3; i < maxn; i += 2)
    if (sieve[i]) {
      primes->pb(i);
    }
  return primes;
}

ll extended_GCD(ll a, ll b, ll &x, ll &y) {
  if (a == 0) {
    x = 0;
    y = 1;
    return b;
  }
  ll x1, y1;
  ll gcd = extended_GCD(b % a, a, x1, y1);
  x = y1 - (b / a) * x1;
  y = x1;
  return gcd;
}

ll ncr(ll n, ll k) {
  ll r = 1;
  if (k > n - k)
    k = n - k;
  for (ll i = 0; i < k; i++) {
    r *= (n - i);
    r /= (i + 1);
  }
  return r;
}

ll power(ll a, ll b, ll m = MOD) {
  ll res = 1;
  while (b > 0) {
    if (b & 1)
      res = (res * a) % m;
    a = (a * a) % m;
    b >>= 1;
  }

  return res;
}

ll modinv(ll a, ll mod = MOD) {
  ll x, y;
  extended_GCD(a, mod, x, y);
  if (x < 0)
    x += mod;
  return x;
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
bool prime(int n) {
  int c = 0;
  for (int i = 2; (i * i) <= n; i++) {
    if (n % i == 0) {
      c++;
      return false;
    }
  }
  if (c == 0)
    return true;
}
// bool compareInterval(char i1, char i2)
//{
//    return (i1 < i2);
//}
// int countoperation(int n,m){
// 	vector<int> d<m+1,-1>;
// }
vector<ll> v[(ll)100001];
ll vis[(ll)100001];
ll c;

void dfs(ll n) {
  vis[n] = 1;
  c++;
  for (ll i : v[n]) {
    if (!vis[i])
      dfs(i);
  }
}
void solve() {

  ll n, e;
  cin >> n >> e;
  forn(i, e) {
    ll a, b;
    cin >> a >> b;
    v[a].pb(b);
    v[b].pb(a);
  }
  ll s = 0;

  for1(i, n) {

    if (!vis[i]) {
      c = 0;
      dfs(i);
      s = max(s, c);
    }
  }

  cout << s << "\\n";
}

int main() {
  flash
  //	freopen("input.txt","r",stdin);
  //	freopen("output.txt","w",stdout);

  //	test
  solve();
  return 0;
}