Problem p03452 (C++)

Buggy submission (status: Runtime Error):
const int N = 505;
const int LG = 21;
const long long MOD = 1e9 + 7;
const long long INF = 1e9;

#include <algorithm>
#include <bitset>
#include <cmath>
#include <deque>
#include <iostream>
#include <map>
#include <set>
#include <string>
#include <time.h>
#include <unordered_set>
#include <vector>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<ll> vi;

#define forn(i, n) for (int(i) = 0; (i) != (n); (i)++)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define popcount(x) __builtin_popcount(x)
#define popcountll(x) __builtin_popcountll(x)
#define fi first
#define se second
#define re return
#define uniq(x)                                                                \
  sort(all(x));                                                                \
  (x).resize(unique(all(x)) - (x).begin())

#ifdef LOCAL
#define dbg(x) cerr << __LINE__ << " " << #x << " " << x << endl
#define ln cerr << __LINE__ << endl
#else
#define dbg(x) void(0)
#define ln void(0)
#endif // LOCAL

int cx[4] = {-1, 0, 1, 0};
int cy[4] = {0, -1, 0, 1};

ll inq(ll x, ll y) {
  if (!y)
    re 1 % MOD;
  ll l = inq(x, y / 2);
  if (y % 2)
    re l *l % MOD *x % MOD;
  re l *l % MOD;
}

ll rev(ll x) { return inq(x, MOD - 2); }

bool __precomputed_combinatorics = 0;
vector<ll> __fact, __ufact, __rev;

void __precompute_combinatorics() {
  __precomputed_combinatorics = 1;
  __fact.resize(N);
  __ufact.resize(N);
  __rev.resize(N);
  __rev[1] = 1;
  for (int i = 2; i < N; i++)
    __rev[i] = MOD - __rev[MOD % i] * (MOD / i) % MOD;
  __fact[0] = 1, __ufact[0] = 1;
  for (int i = 1; i < N; i++)
    __fact[i] = __fact[i - 1] * i % MOD,
    __ufact[i] = __ufact[i - 1] * __rev[i] % MOD;
}

ll fact(int x) {
  if (!__precomputed_combinatorics)
    __precompute_combinatorics();
  return __fact[x];
}

ll cnk(int n, int k) {
  if (!__precomputed_combinatorics)
    __precompute_combinatorics();
  return __fact[n] * __ufact[n - k] % MOD * __ufact[k] % MOD;
}

void __fast_IO() {
#ifdef ONLINE_JUDGE
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
#endif // ONLINE_JUDGE
}

// ##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**
// ##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**

int n, m;
ll dist[N], root[N];
vector<int> sub[N];

int Root(int x) {
  if (x == root[x])
    return x;
  return Root(root[x]);
}

signed main() {
  __fast_IO();
  cin >> n >> m;
  for (int i = 0; i < n; i++)
    root[i] = i, sub[i] = {i};
  for (int i = 0; i < m; i++) {
    int a, b, w;
    cin >> a >> b >> w;
    a--, b--;
    int x = Root(a), y = Root(b);
    if (x == y) {
      if (dist[b] - dist[a] != w) {
        cout << "No";
        return 0;
      }
      continue;
    }
    if (sub[x].size() < sub[y].size()) {
      dist[x] = -dist[a] - w + dist[b];
      for (auto e : sub[x]) {
        sub[y].push_back(e);
        root[e] = y;
        if (e != x)
          dist[e] += dist[x];
      }
    } else {
      dist[y] = dist[a] + w - dist[b];
      for (auto e : sub[y]) {
        sub[x].push_back(e);
        root[e] = x;
        if (e != y)
          dist[e] += dist[y];
      }
    }
  }
  cout << "Yes";
}

/* Note:
Check constants at the beginning of the code.
N is set to 4e5 but be careful in problems with large constant factor.
Check corner cases.
No def int long long for now.
*/


Fixed submission:
const int N = 4e5;
const int LG = 21;
const long long MOD = 1e9 + 7;
const long long INF = 1e9;

#include <algorithm>
#include <bitset>
#include <cmath>
#include <deque>
#include <iostream>
#include <map>
#include <set>
#include <string>
#include <time.h>
#include <unordered_set>
#include <vector>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<ll> vi;

#define forn(i, n) for (int(i) = 0; (i) != (n); (i)++)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define popcount(x) __builtin_popcount(x)
#define popcountll(x) __builtin_popcountll(x)
#define fi first
#define se second
#define re return
#define uniq(x)                                                                \
  sort(all(x));                                                                \
  (x).resize(unique(all(x)) - (x).begin())

#ifdef LOCAL
#define dbg(x) cerr << __LINE__ << " " << #x << " " << x << endl
#define ln cerr << __LINE__ << endl
#else
#define dbg(x) void(0)
#define ln void(0)
#endif // LOCAL

int cx[4] = {-1, 0, 1, 0};
int cy[4] = {0, -1, 0, 1};

ll inq(ll x, ll y) {
  if (!y)
    re 1 % MOD;
  ll l = inq(x, y / 2);
  if (y % 2)
    re l *l % MOD *x % MOD;
  re l *l % MOD;
}

ll rev(ll x) { return inq(x, MOD - 2); }

bool __precomputed_combinatorics = 0;
vector<ll> __fact, __ufact, __rev;

void __precompute_combinatorics() {
  __precomputed_combinatorics = 1;
  __fact.resize(N);
  __ufact.resize(N);
  __rev.resize(N);
  __rev[1] = 1;
  for (int i = 2; i < N; i++)
    __rev[i] = MOD - __rev[MOD % i] * (MOD / i) % MOD;
  __fact[0] = 1, __ufact[0] = 1;
  for (int i = 1; i < N; i++)
    __fact[i] = __fact[i - 1] * i % MOD,
    __ufact[i] = __ufact[i - 1] * __rev[i] % MOD;
}

ll fact(int x) {
  if (!__precomputed_combinatorics)
    __precompute_combinatorics();
  return __fact[x];
}

ll cnk(int n, int k) {
  if (!__precomputed_combinatorics)
    __precompute_combinatorics();
  return __fact[n] * __ufact[n - k] % MOD * __ufact[k] % MOD;
}

void __fast_IO() {
#ifdef ONLINE_JUDGE
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
#endif // ONLINE_JUDGE
}

// ##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**
// ##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**##**

int n, m;
ll dist[N], root[N];
vector<int> sub[N];

int Root(int x) {
  if (x == root[x])
    return x;
  return Root(root[x]);
}

signed main() {
  __fast_IO();
  cin >> n >> m;
  for (int i = 0; i < n; i++)
    root[i] = i, sub[i] = {i};
  for (int i = 0; i < m; i++) {
    int a, b, w;
    cin >> a >> b >> w;
    a--, b--;
    int x = Root(a), y = Root(b);
    if (x == y) {
      if (dist[b] - dist[a] != w) {
        cout << "No";
        return 0;
      }
      continue;
    }
    if (sub[x].size() < sub[y].size()) {
      dist[x] = -dist[a] - w + dist[b];
      for (auto e : sub[x]) {
        sub[y].push_back(e);
        root[e] = y;
        if (e != x)
          dist[e] += dist[x];
      }
    } else {
      dist[y] = dist[a] + w - dist[b];
      for (auto e : sub[y]) {
        sub[x].push_back(e);
        root[e] = x;
        if (e != y)
          dist[e] += dist[y];
      }
    }
  }
  cout << "Yes";
}

/* Note:
Check constants at the beginning of the code.
N is set to 4e5 but be careful in problems with large constant factor.
Check corner cases.
No def int long long for now.
*/