Problem p02573 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#include <iostream>

using namespace std;
#define io                                                                     \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(0);                                                                  \
  cout.tie(0)

#define MOD 1000000007
#define fix(n) cout << fixed << setprecision(n)
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define REP(i, a, b) for (long i = a; i <= b; i++)
#define REN(i, a, b) for (long i = b; i >= a; i--)
// Debugging
#define line cout << endl
#define out(n) cout << n << " "
#define bug(n) cout << n << "\n"
#define print(arr, start, end)                                                 \
  REP(i, start, end) out(arr[i]);                                              \
  line

typedef long long ll;
typedef vector<int> vi;
typedef vector<long long> vll;
typedef pair<int, int> pi;
typedef map<int, int> mii;

///// General Purpose functions /////

////////////////
int util(int s, vector<int> adj[], vector<bool> visited) {
  visited[s] = true;
  queue<int> q;
  q.push(s);
  int l = 0;

  while (!q.empty()) {
    int tmp = q.front();
    l++;
    q.pop();

    for (auto it = adj[tmp].begin(); it != adj[tmp].end(); it++) {
      if (visited[*it] == true)
        continue;
      visited[*it] = true;
      q.push(*it);
    }
  }

  return l;
}

int bfs(vector<int> adj[], int V) {
  int len = 0;
  vector<bool> visited(V, false);

  for (int i = 0; i < V; i++) {
    if (visited[i] == false) {
      int l = util(i, adj, visited);
      len = max(len, l);
    }
  }

  return len;
}

void solve() {
  int V, m;
  cin >> V >> m;
  int x, y;

  vector<int> adj[V];

  for (int i = 0; i < m; i++) {
    cin >> x >> y;
    adj[x - 1].push_back(y - 1);
    adj[y - 1].push_back(x - 1);
  }

  int max_len = bfs(adj, V);
  // out("a\n");
  bug(max_len);
}

void prep() {}

int main() {
  // code
  io;
  int t = 1;
  // cin >> t;
  prep();
  fix(12);
  while (t--) {
    solve();
  }

  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
#include <iostream>

using namespace std;
#define io                                                                     \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(0);                                                                  \
  cout.tie(0)

#define MOD 1000000007
#define fix(n) cout << fixed << setprecision(n)
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define REP(i, a, b) for (long i = a; i <= b; i++)
#define REN(i, a, b) for (long i = b; i >= a; i--)
// Debugging
#define line cout << endl
#define out(n) cout << n << " "
#define bug(n) cout << n << "\n"
#define print(arr, start, end)                                                 \
  REP(i, start, end) out(arr[i]);                                              \
  line

typedef long long ll;
typedef vector<int> vi;
typedef vector<long long> vll;
typedef pair<int, int> pi;
typedef map<int, int> mii;

///// General Purpose functions /////

////////////////
int util(int s, vector<int> adj[], vector<bool> &visited) {
  visited[s] = true;
  queue<int> q;
  q.push(s);
  int l = 0;

  while (!q.empty()) {
    int tmp = q.front();
    l++;
    q.pop();

    for (auto it = adj[tmp].begin(); it != adj[tmp].end(); it++) {
      if (visited[*it] == true)
        continue;
      visited[*it] = true;
      q.push(*it);
    }
  }

  return l;
}

int bfs(vector<int> adj[], int V) {
  int len = 0;
  vector<bool> visited(V, false);

  for (int i = 0; i < V; i++) {
    if (visited[i] == false) {
      int l = util(i, adj, visited);
      len = max(len, l);
    }
  }

  return len;
}

void solve() {
  int V, m;
  cin >> V >> m;
  int x, y;

  vector<int> adj[V];

  for (int i = 0; i < m; i++) {
    cin >> x >> y;
    adj[x - 1].push_back(y - 1);
    adj[y - 1].push_back(x - 1);
  }

  int max_len = bfs(adj, V);
  // out("a\n");
  bug(max_len);
}

void prep() {}

int main() {
  // code
  io;
  int t = 1;
  // cin >> t;
  prep();
  fix(12);
  while (t--) {
    solve();
  }

  return 0;
}