Problem p03955 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
/*#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template<typename T> using gpp_set = tree<T, null_type, less<T>, rb_tree_tag,
tree_order_statistics_node_update>; template<typename T, typename L> using
gpp_map = tree<T, L, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T> using gpp_multiset = tree<T, null_type, less_equal<T>,
rb_tree_tag, tree_order_statistics_node_update>;*/
struct fast_ios {
  fast_ios() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  };
} fast_ios_;
#define FOR(i, begin, end) for (int i = (begin); i < (end); i++)
#define REP(i, n) FOR(i, 0, n)
#define IFOR(i, begin, end) for (int i = (end)-1; i >= (begin); i--)
#define IREP(i, n) IFOR(i, 0, n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(), v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x)                                                      \
  distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x)                                                      \
  distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define Max(a, b) a = max(a, b)
#define Min(a, b) a = min(a, b)
#define bit(n) (1LL << (n))
#define bit_exist(x, n) ((x >> n) & 1)
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v)                                                              \
  {                                                                            \
    cout << #v << "=" << endl;                                                 \
    REP(i_debug, v.size()) { cout << v[i_debug] << ","; }                      \
    cout << endl;                                                              \
  }
#define mdebug(m)                                                              \
  {                                                                            \
    cout << #m << "=" << endl;                                                 \
    REP(i_debug, m.size()) {                                                   \
      REP(j_debug, m[i_debug].size()) { cout << m[i_debug][j_debug] << ","; }  \
      cout << endl;                                                            \
    }                                                                          \
  }
#define Return(ans)                                                            \
  {                                                                            \
    cout << (ans) << endl;                                                     \
    return 0;                                                                  \
  }
#define pb push_back
#define f first
#define s second
#define int long long
#define INF 1000000000000000000
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  for (int i = 0; i < v.size(); i++) {
    cout << v[i];
    if (i != v.size() - 1)
      cout << endl;
  };
  return os;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, pair<T1, T2> p) {
  cout << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T> void Out(T x) { cout << x << endl; }
template <typename T1, typename T2> void Ans(bool f, T1 y, T2 n) {
  if (f)
    Out(y);
  else
    Out(n);
}

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using PiP = pair<int, Pii>;
using PPi = pair<Pii, int>;
using bools = vector<bool>;
using pairs = vector<Pii>;

// int dx[4] = {1,0,-1,0};
// int dy[4] = {0,1,0,-1};
// char d[4] = {'D','R','U','L'};

const int mod = 1000000007;
// const int mod = 998244353;
// #define Add(x, y) x = (x + (y)) % mod
// #define Mult(x, y) x = (x * (y)) % mod

struct SegmentTree {
  using T = int;

  int N;
  vector<T> dat;

  T id = 0;
  T F(T &a, T &b) { return a + b; }

  SegmentTree(int n) {
    N = 1;
    while (n > N)
      N = N << 1;
    dat = vector<T>(2 * N - 1, id);
  }

  SegmentTree(int n, vector<T> &v) {
    N = 1;
    while (n > N)
      N = N << 1;
    dat = vector<T>(2 * N - 1, id);
    for (int i = 0; i < n; i++)
      dat[i + N - 1] = v[i];
    for (int i = N - 2; i >= 0; i--)
      dat[i] = F(dat[i * 2 + 1], dat[i * 2 + 2]);
  }

  SegmentTree() {}

  void update(int k, T a) {
    k += N - 1;
    dat[k] = a;
    while (k > 0) {
      k = (k - 1) / 2;
      dat[k] = F(dat[k * 2 + 1], dat[k * 2 + 2]);
    }
  }

  void reset() { fill(dat.begin(), dat.end(), id); }

  T get(int a, int b, int k, int l, int r) {
    if (r <= a || b <= l)
      return id;
    if (a <= l && r <= b)
      return dat[k];
    else {
      T vl = get(a, b, k * 2 + 1, l, (l + r) / 2);
      T vr = get(a, b, k * 2 + 2, (l + r) / 2, r);
      return F(vl, vr);
    }
  }
  T get(int a, int b) { return get(a, b, 0, 0, N); }

  T val(int k) { return dat[k + N - 1]; }
};

signed main() {

  int N;
  cin >> N;
  assert(N >= 6);
  mat a(3, vec(N));
  cin >> a;

  vec b(N);
  bools flip(N);

  REP(i, N) {
    REP(j, 3) a[j][i]--;
    int x = (a[1][i] - 1) / 3;

    if (a[0][i] == 3 * x && a[1][i] == 3 * x + 1 && a[2][i] == 3 * x + 2)
      flip[i] = false;
    else if (a[2][i] == 3 * x && a[1][i] == 3 * x + 1 && a[0][i] == 3 * x + 2)
      flip[i] = true;
    else {
      Out("No");
      return 0;
    }
    b[i] = x;
    if (b[i] % 2 != i % 2) {
      Out("No");
      return 0;
    }
  }

  vec n(2, 0), m(2, 0);
  REP(k, 2) {
    SegmentTree ST(N);
    for (int i = k; i < N; i += 2) {
      n[k] += ST.get(b[i], N);
      ST.update(b[i], 1);
      if (flip[i])
        m[k]++;
    }
    n[k] %= 2;
    m[k] %= 2;
  }

  Ans(n[0] == m[1] && n[1] == m[0], "Yes", "No");

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
/*#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template<typename T> using gpp_set = tree<T, null_type, less<T>, rb_tree_tag,
tree_order_statistics_node_update>; template<typename T, typename L> using
gpp_map = tree<T, L, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T> using gpp_multiset = tree<T, null_type, less_equal<T>,
rb_tree_tag, tree_order_statistics_node_update>;*/
struct fast_ios {
  fast_ios() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  };
} fast_ios_;
#define FOR(i, begin, end) for (int i = (begin); i < (end); i++)
#define REP(i, n) FOR(i, 0, n)
#define IFOR(i, begin, end) for (int i = (end)-1; i >= (begin); i--)
#define IREP(i, n) IFOR(i, 0, n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(), v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x)                                                      \
  distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x)                                                      \
  distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define Max(a, b) a = max(a, b)
#define Min(a, b) a = min(a, b)
#define bit(n) (1LL << (n))
#define bit_exist(x, n) ((x >> n) & 1)
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v)                                                              \
  {                                                                            \
    cout << #v << "=" << endl;                                                 \
    REP(i_debug, v.size()) { cout << v[i_debug] << ","; }                      \
    cout << endl;                                                              \
  }
#define mdebug(m)                                                              \
  {                                                                            \
    cout << #m << "=" << endl;                                                 \
    REP(i_debug, m.size()) {                                                   \
      REP(j_debug, m[i_debug].size()) { cout << m[i_debug][j_debug] << ","; }  \
      cout << endl;                                                            \
    }                                                                          \
  }
#define Return(ans)                                                            \
  {                                                                            \
    cout << (ans) << endl;                                                     \
    return 0;                                                                  \
  }
#define pb push_back
#define f first
#define s second
#define int long long
#define INF 1000000000000000000
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  for (int i = 0; i < v.size(); i++) {
    cout << v[i];
    if (i != v.size() - 1)
      cout << endl;
  };
  return os;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, pair<T1, T2> p) {
  cout << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T> void Out(T x) { cout << x << endl; }
template <typename T1, typename T2> void Ans(bool f, T1 y, T2 n) {
  if (f)
    Out(y);
  else
    Out(n);
}

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using PiP = pair<int, Pii>;
using PPi = pair<Pii, int>;
using bools = vector<bool>;
using pairs = vector<Pii>;

// int dx[4] = {1,0,-1,0};
// int dy[4] = {0,1,0,-1};
// char d[4] = {'D','R','U','L'};

const int mod = 1000000007;
// const int mod = 998244353;
// #define Add(x, y) x = (x + (y)) % mod
// #define Mult(x, y) x = (x * (y)) % mod

struct SegmentTree {
  using T = int;

  int N;
  vector<T> dat;

  T id = 0;
  T F(T &a, T &b) { return a + b; }

  SegmentTree(int n) {
    N = 1;
    while (n > N)
      N = N << 1;
    dat = vector<T>(2 * N - 1, id);
  }

  SegmentTree(int n, vector<T> &v) {
    N = 1;
    while (n > N)
      N = N << 1;
    dat = vector<T>(2 * N - 1, id);
    for (int i = 0; i < n; i++)
      dat[i + N - 1] = v[i];
    for (int i = N - 2; i >= 0; i--)
      dat[i] = F(dat[i * 2 + 1], dat[i * 2 + 2]);
  }

  SegmentTree() {}

  void update(int k, T a) {
    k += N - 1;
    dat[k] = a;
    while (k > 0) {
      k = (k - 1) / 2;
      dat[k] = F(dat[k * 2 + 1], dat[k * 2 + 2]);
    }
  }

  void reset() { fill(dat.begin(), dat.end(), id); }

  T get(int a, int b, int k, int l, int r) {
    if (r <= a || b <= l)
      return id;
    if (a <= l && r <= b)
      return dat[k];
    else {
      T vl = get(a, b, k * 2 + 1, l, (l + r) / 2);
      T vr = get(a, b, k * 2 + 2, (l + r) / 2, r);
      return F(vl, vr);
    }
  }
  T get(int a, int b) { return get(a, b, 0, 0, N); }

  T val(int k) { return dat[k + N - 1]; }
};

signed main() {

  int N;
  cin >> N;
  mat a(3, vec(N));
  cin >> a;

  vec b(N);
  bools flip(N);

  REP(i, N) {
    REP(j, 3) a[j][i]--;
    int x = (a[1][i] - 1) / 3;

    if (a[0][i] == 3 * x && a[1][i] == 3 * x + 1 && a[2][i] == 3 * x + 2)
      flip[i] = false;
    else if (a[2][i] == 3 * x && a[1][i] == 3 * x + 1 && a[0][i] == 3 * x + 2)
      flip[i] = true;
    else {
      Out("No");
      return 0;
    }
    b[i] = x;
    if (b[i] % 2 != i % 2) {
      Out("No");
      return 0;
    }
  }

  vec n(2, 0), m(2, 0);
  REP(k, 2) {
    SegmentTree ST(N);
    for (int i = k; i < N; i += 2) {
      n[k] += ST.get(b[i], N);
      ST.update(b[i], 1);
      if (flip[i])
        m[k]++;
    }
    n[k] %= 2;
    m[k] %= 2;
  }

  Ans(n[0] == m[1] && n[1] == m[0], "Yes", "No");

  return 0;
}