Problem p02540 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef vector<ll> vi;
typedef vector<pll> vpll;
const ll infl = 0x3f3f3f3f3f3f3f3fLL;
const int infi = 0x3f3f3f3f;
#define endl '\\n'
#define pb push_back
#define all(a) (a).begin(), (a).end()
#define F first
#define S second
#define rs(v, n) v.resize(n)
#define hell 1000000007
// #define hell        998244353
#define peak 9e18
#define pii acos(-1)
#define clr(a, x) memset(a, x, sizeof(a))
auto clk = clock();
mt19937_64
    rang(chrono::high_resolution_clock::now().time_since_epoch().count());

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template <typename T>
using ordered_set =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

namespace Ops {
template <class y, class z> z expo(ll b, y e, z m) {
  ll a = 1;
  b %= m;
  while (e != 0) {
    if ((e & 1) == 1) {
      a = a * b;
      a = a % m;
    }
    b = b * b;
    b %= m;
    e >>= 1;
  }
  return a % m;
}
template <class y, class z> z power(ll b, y e) {
  ll a = 1;
  while (e != 0) {
    if ((e & 1) == 1) {
      a = a * b;
    }
    b = b * b;
    e >>= 1;
  }
  return a;
}
template <class x, class z> z inv(x b, z m) { return expo(b, m - 2, m); }
template <class x, class y> x invGeneral(x a, y b) {
  if (a == 0)
    return b == 1 ? 0 : -1;
  x m = invGeneral(b % a, a);
  return m == -1 ? -1 : ((1 - (ll)b * m) / a + b) % b;
}
template <class x, class y> x min(x a, y b) {
  x c;
  if (a <= b)
    c = a;
  else
    c = b;
  return c;
}
template <class x, class y> x max(x a, y b) {
  x c;
  if (a >= b)
    c = a;
  else
    c = b;
  return c;
}
} // namespace Ops
using namespace Ops;

namespace InOp {
template <class x> istream &operator>>(istream &in, vector<x> &v) {
  for (auto &i : v)
    in >> i;
  return in;
}
template <class x, class y> ostream &operator<<(ostream &out, pair<x, y> &p) {
  out << "(" << p.F << "," << p.S << ")";
  return out;
}
template <class x> ostream &operator<<(ostream &out, vector<x> &v) {
  out << "Size : " << v.size() << endl;
  for (auto i : v)
    out << i << " ";
  out << endl;
  return out;
}
} // namespace InOp
using namespace InOp;

namespace Debug {
#define LOCAL
#ifdef LOCAL
#define deb(...) printall(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void printall(const char *name, Arg1 &&arg1) {
  cerr << name << " : " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void printall(const char *names, Arg1 &&arg1, Args &&...args) {
  const char *comma = strchr(names, ',');
  cerr.write(names, comma - names) << " : " << arg1 << " | ";
  printall(comma + 1, args...);
}
#else
#define deb(...) void(0)
#endif
} // namespace Debug
using namespace Debug;

namespace Bits {
template <class x> constexpr int onbits(x a) { return __builtin_popcount(a); }
constexpr int bits(long long x) {
  return 64 - __builtin_clzll(x);
} // take care of 0
constexpr int bits(int x) { return 32 - __builtin_clz(x); } // take care of 0
constexpr int traz(int a) { return __builtin_ctz(a); }
constexpr int traz(long long a) { return __builtin_ctzll(a); }
} // namespace Bits
using namespace Bits;

namespace YesNo {
// #define CAPITAL
void yes() {
#ifdef CAPITAL
  cout << "YES"
       << "\\n";
#else
  cout << "Yes"
       << "\\n";
#endif
}
void no() {
#ifdef CAPITAL
  cout << "NO"
       << "\\n";
#else
  cout << "No"
       << "\\n";
#endif
}
} // namespace YesNo
using namespace YesNo;

void maester();
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  srand(chrono::high_resolution_clock::now().time_since_epoch().count());
  cout << fixed << setprecision(6);
  ll test = 1;
  // cin>>test;
  while (test--) {
    maester();
  }
#ifndef ONLINE_JUDGE
  cout << endl
       << endl
       << endl
       << endl
       << "Time elapsed: " << (double)(clock() - clk) / CLOCKS_PER_SEC << endl;
#endif
  return 0;
}
#define N 200005
vi pa(N), sz(N);
ll findpa(ll x) {
  ll y = pa[x];
  if (y == x)
    return y;
  pa[x] = findpa(y);
  return pa[x];
}
void connect(ll x, ll y) {
  // deb(x,y);
  ll px = findpa(x);
  ll py = findpa(y);
  if (px < py)
    swap(px, py);
  pa[px] = py;
  sz[py] += sz[px];
}
void maester() {
  ll i, j, k, l, r, m, n, x, y;
  cin >> n;
  for (i = 0; i <= n; i++)
    pa[i] = i, sz[i] = 1;
  vector<pair<ll, pair<ll, ll>>> v;
  for (i = 0; i < n; i++) {
    cin >> x >> y;
    v.pb({x, {y, i}});
  }
  sort(all(v));
  // deb(v);
  vi vv(n);
  for (i = 0; i < n; i++)
    vv[i] = v[i].S.F;
  set<ll> s;
  for (i = 0; i < n; i++) {
    vi vp;
    for (auto j : s) {
      if (j > vv[i])
        break;
      vp.pb(j);
      connect(j, vv[i]);
    }
    for (auto j : vp)
      s.erase(j);
    x = findpa(vv[i]);
    s.insert(x);
  }
  // deb(sz,pa);
  vi ans(n);
  for (i = 0; i < n; i++) {
    ans[v[i].S.S] = sz[findpa(v[i].S.F)];
  }
  for (i = 0; i < n; i++)
    cout << ans[i] << endl;
}

Error: WA

Fixed submission:

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef vector<ll> vi;
typedef vector<pll> vpll;
const ll infl = 0x3f3f3f3f3f3f3f3fLL;
const int infi = 0x3f3f3f3f;
#define endl '\\n'
#define pb push_back
#define all(a) (a).begin(), (a).end()
#define F first
#define S second
#define rs(v, n) v.resize(n)
#define hell 1000000007
// #define hell        998244353
#define peak 9e18
#define pii acos(-1)
#define clr(a, x) memset(a, x, sizeof(a))
auto clk = clock();
mt19937_64
    rang(chrono::high_resolution_clock::now().time_since_epoch().count());

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template <typename T>
using ordered_set =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

namespace Ops {
template <class y, class z> z expo(ll b, y e, z m) {
  ll a = 1;
  b %= m;
  while (e != 0) {
    if ((e & 1) == 1) {
      a = a * b;
      a = a % m;
    }
    b = b * b;
    b %= m;
    e >>= 1;
  }
  return a % m;
}
template <class y, class z> z power(ll b, y e) {
  ll a = 1;
  while (e != 0) {
    if ((e & 1) == 1) {
      a = a * b;
    }
    b = b * b;
    e >>= 1;
  }
  return a;
}
template <class x, class z> z inv(x b, z m) { return expo(b, m - 2, m); }
template <class x, class y> x invGeneral(x a, y b) {
  if (a == 0)
    return b == 1 ? 0 : -1;
  x m = invGeneral(b % a, a);
  return m == -1 ? -1 : ((1 - (ll)b * m) / a + b) % b;
}
template <class x, class y> x min(x a, y b) {
  x c;
  if (a <= b)
    c = a;
  else
    c = b;
  return c;
}
template <class x, class y> x max(x a, y b) {
  x c;
  if (a >= b)
    c = a;
  else
    c = b;
  return c;
}
} // namespace Ops
using namespace Ops;

namespace InOp {
template <class x> istream &operator>>(istream &in, vector<x> &v) {
  for (auto &i : v)
    in >> i;
  return in;
}
template <class x, class y> ostream &operator<<(ostream &out, pair<x, y> &p) {
  out << "(" << p.F << "," << p.S << ")";
  return out;
}
template <class x> ostream &operator<<(ostream &out, vector<x> &v) {
  out << "Size : " << v.size() << endl;
  for (auto i : v)
    out << i << " ";
  out << endl;
  return out;
}
} // namespace InOp
using namespace InOp;

namespace Debug {
#define LOCAL
#ifdef LOCAL
#define deb(...) printall(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void printall(const char *name, Arg1 &&arg1) {
  cerr << name << " : " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void printall(const char *names, Arg1 &&arg1, Args &&...args) {
  const char *comma = strchr(names, ',');
  cerr.write(names, comma - names) << " : " << arg1 << " | ";
  printall(comma + 1, args...);
}
#else
#define deb(...) void(0)
#endif
} // namespace Debug
using namespace Debug;

namespace Bits {
template <class x> constexpr int onbits(x a) { return __builtin_popcount(a); }
constexpr int bits(long long x) {
  return 64 - __builtin_clzll(x);
} // take care of 0
constexpr int bits(int x) { return 32 - __builtin_clz(x); } // take care of 0
constexpr int traz(int a) { return __builtin_ctz(a); }
constexpr int traz(long long a) { return __builtin_ctzll(a); }
} // namespace Bits
using namespace Bits;

namespace YesNo {
// #define CAPITAL
void yes() {
#ifdef CAPITAL
  cout << "YES"
       << "\\n";
#else
  cout << "Yes"
       << "\\n";
#endif
}
void no() {
#ifdef CAPITAL
  cout << "NO"
       << "\\n";
#else
  cout << "No"
       << "\\n";
#endif
}
} // namespace YesNo
using namespace YesNo;

void maester();
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  srand(chrono::high_resolution_clock::now().time_since_epoch().count());
  cout << fixed << setprecision(6);
  ll test = 1;
  // cin>>test;
  while (test--) {
    maester();
  }
#ifndef ONLINE_JUDGE
  cout << endl
       << endl
       << endl
       << endl
       << "Time elapsed: " << (double)(clock() - clk) / CLOCKS_PER_SEC << endl;
#endif
  return 0;
}
#define N 25
vi pa(N), sz(N);
ll findpa(ll x) {
  ll y = pa[x];
  if (y == x)
    return y;
  pa[x] = findpa(y);
  return pa[x];
}
void connect(ll x, ll y) {
  // deb(x,y);
  ll px = findpa(x);
  ll py = findpa(y);
  if (px < py)
    swap(px, py);
  pa[px] = py;
  sz[py] += sz[px];
}
void maester() {
  ll i, j, k, l, r, m, n, x, y;
  cin >> n;
  for (i = 0; i <= n; i++)
    pa[i] = i, sz[i] = 1;
  vector<pair<ll, pair<ll, ll>>> v;
  for (i = 0; i < n; i++) {
    cin >> x >> y;
    v.pb({x, {y, i}});
  }
  sort(all(v));
  // deb(v);
  vi vv(n);
  for (i = 0; i < n; i++)
    vv[i] = v[i].S.F;
  set<ll> s;
  for (i = 0; i < n; i++) {
    vi vp;
    for (auto j : s) {
      if (j > vv[i])
        break;
      vp.pb(j);
      connect(j, vv[i]);
    }
    for (auto j : vp)
      s.erase(j);
    x = findpa(vv[i]);
    s.insert(x);
  }
  // deb(sz,pa);
  vi ans(n);
  for (i = 0; i < n; i++) {
    ans[v[i].S.S] = sz[findpa(v[i].S.F)];
  }
  for (i = 0; i < n; i++)
    cout << ans[i] << endl;
}