Problem p02692 (C++)

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

#define rep(i, n) for (int i = 0; i < int(n); i++)
#define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define reps(i, n) for (int i = 1; i <= int(n); i++)
#define rreps(i, n) for (int i = int(n); i >= 1; i--)
#define repc(i, n) for (int i = 0; i <= int(n); i++)
#define rrepc(i, n) for (int i = int(n); i >= 0; i--)
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define repic(i, a, b) for (int i = int(a); i <= int(b); i++)
#define each(x, y) for (auto &x : y)
#define all(a) (a).begin(), (a).end()
#define bit32(x) (1 << (x))
#define bit64(x) (1ll << (x))
#define sz(v) ((int)v.size())

using namespace std;

using i64 = long long;
using f80 = long double;
using vi32 = vector<int>;
using vi64 = vector<i64>;
using vf80 = vector<f80>;
using vstr = vector<string>;

inline void yes() {
  cout << "Yes" << endl;
  exit(0);
}
inline void no() {
  cout << "No" << endl;
  exit(0);
}
inline i64 gcd(i64 a, i64 b) {
  if (min(a, b) == 0)
    return max(a, b);
  if (a % b == 0)
    return b;
  return gcd(b, a % b);
}
inline i64 lcm(i64 a, i64 b) {
  if (min(a, b) == 0)
    return max(a, b);
  return a / gcd(a, b) * b;
}
template <typename T>
class pqasc : public priority_queue<T, vector<T>, greater<T>> {};
template <typename T>
class pqdesc : public priority_queue<T, vector<T>, less<T>> {};
template <typename T> inline void amax(T &x, T y) { x = max(x, y); }
template <typename T> inline void amin(T &x, T y) { x = min(x, y); }
template <typename T> inline T exp(T x, i64 n, T e = 1) {
  T r = e;
  while (n > 0) {
    if (n & 1)
      r *= x;
    x *= x;
    n >>= 1;
  }
  return r;
}
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  each(x, v) is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  rep(i, v.size()) {
    if (i)
      os << ' ';
    os << v[i];
  }
  return os;
}
void solve();
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout << fixed << setprecision(16);
  solve();
  return 0;
}

int dpl[100001][4][4][4];

void solve() {
  int n, a, b, c;
  cin >> n >> a >> b >> c;
  vstr s(n);
  cin >> s;
  amin(a, 2);
  amin(b, 2);
  amin(c, 2);
  dpl[0][a][b][c] = 1;
  rep(i, n) repc(j, 3) repc(k, 3) repc(l, 3) {
    if (dpl[i][j][k][l] == 0)
      continue;
    if (s[i] == "AB") {
      if (j > 0)
        dpl[i + 1][j - 1][k + 1][l] = 1;
      if (k > 0)
        dpl[i + 1][j + 1][k - 1][l] = 1;
    } else if (s[i] == "BC") {
      if (k > 0)
        dpl[i + 1][j][k - 1][l + 1] = 1;
      if (l > 0)
        dpl[i + 1][j][k + 1][l - 1] = 1;
    } else {
      if (j > 0)
        dpl[i + 1][j - 1][k][l + 1] = 1;
      if (l > 0)
        dpl[i + 1][j + 1][k][l - 1] = 1;
    }
  }
  bool ok = false;
  int nj, nk, nl;
  repc(j, 3) repc(k, 3) repc(l, 3) {
    if (!ok && dpl[n][j][k][l]) {
      ok = true;
      nj = j, nk = k, nl = l;
    }
  }
  if (!ok) {
    cout << "No" << endl;
    return;
  }
  string ans;
  while (sz(ans) < n) {
    int i = n - sz(ans) - 1;
    int j = nj, k = nk, l = nl;
    if (s[i] == "AB") {
      if (j > 0 && dpl[i][j - 1][k + 1][l]) {
        nj = j - 1, nk = k + 1, nl = l, ans += 'A';
      } else if (k > 0 && dpl[i][j + 1][k - 1][l]) {
        nj = j + 1, nk = k - 1, nl = l, ans += 'B';
      }
    } else if (s[i] == "BC") {
      if (k > 0 && dpl[i][j][k - 1][l + 1]) {
        nj = j, nk = k - 1, nl = l + 1, ans += 'B';
      } else if (l > 0 && dpl[i][j][k + 1][l - 1]) {
        nj = j, nk = k + 1, nl = l - 1, ans += 'C';
      }
    } else {
      if (j > 0 && dpl[i][j - 1][k][l + 1]) {
        nj = j - 1, nk = k, nl = l + 1, ans += 'A';
      } else if (l > 0 && dpl[i][j + 1][k][l - 1]) {
        nj = j + 1, nk = k, nl = l - 1, ans += 'C';
      }
    }
  }
  cout << "Yes" << endl;
  reverse(all(ans));
  rep(i, n) { cout << ans[i] << endl; }
}


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

#define rep(i, n) for (int i = 0; i < int(n); i++)
#define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define reps(i, n) for (int i = 1; i <= int(n); i++)
#define rreps(i, n) for (int i = int(n); i >= 1; i--)
#define repc(i, n) for (int i = 0; i <= int(n); i++)
#define rrepc(i, n) for (int i = int(n); i >= 0; i--)
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define repic(i, a, b) for (int i = int(a); i <= int(b); i++)
#define each(x, y) for (auto &x : y)
#define all(a) (a).begin(), (a).end()
#define bit32(x) (1 << (x))
#define bit64(x) (1ll << (x))
#define sz(v) ((int)v.size())

using namespace std;

using i64 = long long;
using f80 = long double;
using vi32 = vector<int>;
using vi64 = vector<i64>;
using vf80 = vector<f80>;
using vstr = vector<string>;

inline void yes() {
  cout << "Yes" << endl;
  exit(0);
}
inline void no() {
  cout << "No" << endl;
  exit(0);
}
inline i64 gcd(i64 a, i64 b) {
  if (min(a, b) == 0)
    return max(a, b);
  if (a % b == 0)
    return b;
  return gcd(b, a % b);
}
inline i64 lcm(i64 a, i64 b) {
  if (min(a, b) == 0)
    return max(a, b);
  return a / gcd(a, b) * b;
}
template <typename T>
class pqasc : public priority_queue<T, vector<T>, greater<T>> {};
template <typename T>
class pqdesc : public priority_queue<T, vector<T>, less<T>> {};
template <typename T> inline void amax(T &x, T y) { x = max(x, y); }
template <typename T> inline void amin(T &x, T y) { x = min(x, y); }
template <typename T> inline T exp(T x, i64 n, T e = 1) {
  T r = e;
  while (n > 0) {
    if (n & 1)
      r *= x;
    x *= x;
    n >>= 1;
  }
  return r;
}
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  each(x, v) is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  rep(i, v.size()) {
    if (i)
      os << ' ';
    os << v[i];
  }
  return os;
}
void solve();
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout << fixed << setprecision(16);
  solve();
  return 0;
}

int dpl[100001][5][5][5];

void solve() {
  int n, a, b, c;
  cin >> n >> a >> b >> c;
  vstr s(n);
  cin >> s;
  amin(a, 2);
  amin(b, 2);
  amin(c, 2);
  dpl[0][a][b][c] = 1;
  rep(i, n) repc(j, 3) repc(k, 3) repc(l, 3) {
    if (dpl[i][j][k][l] == 0)
      continue;
    if (s[i] == "AB") {
      if (j > 0)
        dpl[i + 1][j - 1][k + 1][l] = 1;
      if (k > 0)
        dpl[i + 1][j + 1][k - 1][l] = 1;
    } else if (s[i] == "BC") {
      if (k > 0)
        dpl[i + 1][j][k - 1][l + 1] = 1;
      if (l > 0)
        dpl[i + 1][j][k + 1][l - 1] = 1;
    } else {
      if (j > 0)
        dpl[i + 1][j - 1][k][l + 1] = 1;
      if (l > 0)
        dpl[i + 1][j + 1][k][l - 1] = 1;
    }
  }
  bool ok = false;
  int nj, nk, nl;
  repc(j, 3) repc(k, 3) repc(l, 3) {
    if (!ok && dpl[n][j][k][l]) {
      ok = true;
      nj = j, nk = k, nl = l;
    }
  }
  if (!ok) {
    cout << "No" << endl;
    return;
  }
  string ans;
  while (sz(ans) < n) {
    int i = n - sz(ans) - 1;
    int j = nj, k = nk, l = nl;
    if (s[i] == "AB") {
      if (j > 0 && dpl[i][j - 1][k + 1][l]) {
        nj = j - 1, nk = k + 1, nl = l, ans += 'A';
      } else if (k > 0 && dpl[i][j + 1][k - 1][l]) {
        nj = j + 1, nk = k - 1, nl = l, ans += 'B';
      }
    } else if (s[i] == "BC") {
      if (k > 0 && dpl[i][j][k - 1][l + 1]) {
        nj = j, nk = k - 1, nl = l + 1, ans += 'B';
      } else if (l > 0 && dpl[i][j][k + 1][l - 1]) {
        nj = j, nk = k + 1, nl = l - 1, ans += 'C';
      }
    } else {
      if (j > 0 && dpl[i][j - 1][k][l + 1]) {
        nj = j - 1, nk = k, nl = l + 1, ans += 'A';
      } else if (l > 0 && dpl[i][j + 1][k][l - 1]) {
        nj = j + 1, nk = k, nl = l - 1, ans += 'C';
      }
    }
  }
  cout << "Yes" << endl;
  reverse(all(ans));
  rep(i, n) { cout << ans[i] << endl; }
}