Problem p02998 (C++)

Buggy submission (status: Runtime Error):
// template version 1.12
using namespace std;
#include <bits/stdc++.h>
#include <iostream>

// varibable settings
#define infile "../test/sample-1.in"
#define int long long //{{{
const int INF = 1e18;
const int MOD = 1e9 + 7; //}}}

// define basic macro {{{
#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define _rrep(i, n) rrepi(i, 0, n)
#define rrepi(i, a, b) for (int i = (int)((b)-1); i >= (int)(a); --i)
#define rrep(...) _overload3(__VA_ARGS__, rrepi, _rrep, )(__VA_ARGS__)
#define each(i, a) for (auto &&i : a)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define uni(x)                                                                 \
  sort(all(x));                                                                \
  x.erase(unique(all(x)), x.end())
#define ub upper_bound
#define lb lower_bound
#define posl(A, x) (lower_bound(all(A), x) - A.begin())
#define posu(A, x) (upper_bound(all(A), x) - A.begin())
template <class T> inline void chmax(T &a, const T &b) {
  if ((a) < (b))
    (a) = (b);
}
template <class T> inline void chmin(T &a, const T &b) {
  if ((a) > (b))
    (a) = (b);
}

typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef long double ld;
typedef pair<int, int> pii;
typedef tuple<int, int, int> iii;

template <typename T> using PQ = priority_queue<T, vector<T>, greater<T>>;
struct Fast {
  Fast() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
  }
} fast;

#if defined(PCM) || defined(LOCAL)
#include "lib/dump.hpp"
#else
#define dump(...) 42
#define dump_1d(...) 42
#define dump_2d(...) 42
#endif
//}}}

struct UnionFind {  /*{{{*/
  vector<int> data; // size defined only for root node
  int count;

  UnionFind(int size) : data(size, -1), count(size) {}

  bool merge(int x, int y) {
    x = root(x);
    y = root(y);
    if (x != y) {
      if (data[y] < data[x])
        swap(x, y);
      data[x] += data[y];
      data[y] = x;
      count--;
    }
    return x != y;
  }
  int root(int x) { return (data[x] < 0 ? x : data[x] = root(data[x])); }
  bool same(int x, int y) { return root(x) == root(y); }
  int size(int x) { return -data[root(x)]; }
}; /*}}}*/

#define MAXN 30

struct kousi {
  int x, y, cnt;
};

int solve() {
  int n;
  cin >> n;
  vi x(n), y(n);
  UnionFind uf(200001);

  vvi Y(MAXN + 1, vi());
  vvi X(MAXN + 1, vi());

  rep(i, n) {
    cin >> x[i] >> y[i];
    uf.merge(x[i], y[i] + MAXN);
    Y[y[i]].pb(x[i]);
    X[x[i]].pb(y[i]);
  }
  each(el, Y) {
    rep(i, 1, sz(el)) { uf.merge(el[i - 1], el[i]); }
  }
  each(el, X) {
    rep(i, 1, sz(el)) { uf.merge(el[i - 1] + MAXN, el[i] + MAXN); }
  }
  map<int, kousi> roots;
  rep(i, 1, MAXN + 1) { roots[uf.root(i)].x += 1; }
  rep(i, 1, MAXN + 1) { roots[uf.root(i + MAXN)].y += 1; }
  rep(i, n) { roots[uf.root(x[i])].cnt++; }

  int res = 0;
  each(root, roots) {
    kousi k = root.second;
    // dump(p, k.x, k.y, k.cnt);
    res += k.x * k.y - k.cnt;
  }
  cout << res << endl;

  return 0;
}

signed main() { //{{{
#ifdef INPUT_FROM_FILE
  std::ifstream in(infile);
  std::cin.rdbuf(in.rdbuf());
#endif
  solve();
  return 0;
} //}}}


Fixed submission:
// template version 1.12
using namespace std;
#include <bits/stdc++.h>
#include <iostream>

// varibable settings
#define infile "../test/sample-1.in"
#define int long long //{{{
const int INF = 1e18;
const int MOD = 1e9 + 7; //}}}

// define basic macro {{{
#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define _rrep(i, n) rrepi(i, 0, n)
#define rrepi(i, a, b) for (int i = (int)((b)-1); i >= (int)(a); --i)
#define rrep(...) _overload3(__VA_ARGS__, rrepi, _rrep, )(__VA_ARGS__)
#define each(i, a) for (auto &&i : a)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define uni(x)                                                                 \
  sort(all(x));                                                                \
  x.erase(unique(all(x)), x.end())
#define ub upper_bound
#define lb lower_bound
#define posl(A, x) (lower_bound(all(A), x) - A.begin())
#define posu(A, x) (upper_bound(all(A), x) - A.begin())
template <class T> inline void chmax(T &a, const T &b) {
  if ((a) < (b))
    (a) = (b);
}
template <class T> inline void chmin(T &a, const T &b) {
  if ((a) > (b))
    (a) = (b);
}

typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef long double ld;
typedef pair<int, int> pii;
typedef tuple<int, int, int> iii;

template <typename T> using PQ = priority_queue<T, vector<T>, greater<T>>;
struct Fast {
  Fast() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
  }
} fast;

#if defined(PCM) || defined(LOCAL)
#include "lib/dump.hpp"
#else
#define dump(...) 42
#define dump_1d(...) 42
#define dump_2d(...) 42
#endif
//}}}

struct UnionFind {  /*{{{*/
  vector<int> data; // size defined only for root node
  int count;

  UnionFind(int size) : data(size, -1), count(size) {}

  bool merge(int x, int y) {
    x = root(x);
    y = root(y);
    if (x != y) {
      if (data[y] < data[x])
        swap(x, y);
      data[x] += data[y];
      data[y] = x;
      count--;
    }
    return x != y;
  }
  int root(int x) { return (data[x] < 0 ? x : data[x] = root(data[x])); }
  bool same(int x, int y) { return root(x) == root(y); }
  int size(int x) { return -data[root(x)]; }
}; /*}}}*/

#define MAXN 100000

struct kousi {
  int x, y, cnt;
};

int solve() {
  int n;
  cin >> n;
  vi x(n), y(n);
  UnionFind uf(200001);

  vvi Y(MAXN + 1, vi());
  vvi X(MAXN + 1, vi());

  rep(i, n) {
    cin >> x[i] >> y[i];
    uf.merge(x[i], y[i] + MAXN);
    Y[y[i]].pb(x[i]);
    X[x[i]].pb(y[i]);
  }
  each(el, Y) {
    rep(i, 1, sz(el)) { uf.merge(el[i - 1], el[i]); }
  }
  each(el, X) {
    rep(i, 1, sz(el)) { uf.merge(el[i - 1] + MAXN, el[i] + MAXN); }
  }
  map<int, kousi> roots;
  rep(i, 1, MAXN + 1) { roots[uf.root(i)].x += 1; }
  rep(i, 1, MAXN + 1) { roots[uf.root(i + MAXN)].y += 1; }
  rep(i, n) { roots[uf.root(x[i])].cnt++; }

  int res = 0;
  each(root, roots) {
    kousi k = root.second;
    // dump(p, k.x, k.y, k.cnt);
    res += k.x * k.y - k.cnt;
  }
  cout << res << endl;

  return 0;
}

signed main() { //{{{
#ifdef INPUT_FROM_FILE
  std::ifstream in(infile);
  std::cin.rdbuf(in.rdbuf());
#endif
  solve();
  return 0;
} //}}}