Problem p03165 (C++)

Buggy submission (status: Runtime Error):
#include "bits/stdc++.h"

using ll = long long;

using namespace std;

// 0 -> a-1
#define rep(i, a) for (int i = 0; (i) < (int)(a); (i)++)
// a -> b-1
#define reps(i, a, b) for (int i = (int)(a); (i) < (int)(b); (i)++)
// a-1 -> 0
#define rrep(i, a) for (int i = (int)a - 1; (i) >= 0; (i)--)
// a-1 -> b
#define rreps(i, a, b) for (int i = (int)(a)-1; (i) >= (int)(b); (i)--)
#define MP(a, b) make_pair((a), (b))
#define PB(a) push_back((a))
#define all(v) (v).begin(), (v).end()
// next_permutation(all(v))
#define PERM(v) next_permutation(all(v))
/*sort(all(v));
(v).erase(unique(all(v)), v.end())*/
#define UNIQUE(v)                                                              \
  sort(all(v));                                                                \
  (v).erase(unique(all(v)), v.end())
#define CIN(type, x)                                                           \
  type x;                                                                      \
  cin >> x
#define YES(f)                                                                 \
  if ((f)) {                                                                   \
    cout << "YES" << endl;                                                     \
  } else {                                                                     \
    cout << "NO" << endl;                                                      \
  }
#define Yes(f)                                                                 \
  if ((f)) {                                                                   \
    cout << "Yes" << endl;                                                     \
  } else {                                                                     \
    cout << "No" << endl;                                                      \
  }
#define MINV(v) min_element(all(v))
#define MAXV(v) max_element(all(v))
#define MIN3(a, b, c) min(min(a, b), c)
#define MIN4(a, b, c, d) min(MIN3(a, b, c), d)
#define MIN5(a, b, c, d, e) min(MIN4(a, b, c, d), e)
#define MIN6(a, b, c, d, e, f) min(MIN5(a, b, c, d, e), f)
#define MAX3(a, b, c) max(max(a, b), c)
#define MAX4(a, b, c, d) max(MAX3(a, b, c), d)
#define MAX5(a, b, c, d, e) max(MAX4(a, b, c, d), e)
#define MAX6(a, b, c, d, e, f) max(MAX5(a, b, c, d, e), f)
// b is [a, c)
#define RANGE(a, b, c) ((a) <= (b) && (b) < (c))
// c is [a, e) && d is [b, f)
#define RANGE2D(a, b, c, d, e, f) (RANGE((a), (c), (e)) && RANGE((b), (d), (f)))
#define chmin(a, b) a = min(a, (b))
#define chmin3(a, b, c) a = MIN3(a, (b), (c))
#define chmin4(a, b, c, d) a = MIN4(a, (b), (c), (d))
#define chmin5(a, b, c, d, e) a = MIN5(a, (b), (c), (d), (e))
#define chmin6(a, b, c, d, e, f) a = MIN6(a, (b), (c), (d), (e), (f))
#define chmax(a, b) a = max(a, (b))
#define chmax3(a, b, c) a = MAX3(a, (b), (c))
#define chmax4(a, b, c, d) a = MAX4(a, (b), (c), (d))
#define chmax5(a, b, c, d, e) a = MAX5(a, (b), (c), (d), (e))
#define chmax6(a, b, c, d, e, f) a = MAX6(a, (b), (c), (d), (e), (f))
#define fcout cout << fixed << setprecision(12)
#define RS resize
#define CINV(v, N)                                                             \
  do {                                                                         \
    v.RS(N);                                                                   \
    rep(i, N) cin >> v[i];                                                     \
  } while (0);

#define RCINV(v, N)                                                            \
  do {                                                                         \
    v.RS(N);                                                                   \
    rrep(i, N) cin >> v[i];                                                    \
  } while (0);
#define MOD 1000000007

template <class T> inline T GET() {
  T x;
  cin >> x;
  return x;
}

void init();
void solve();

signed main() {
  init();
  solve();
}

int dp[3123][3123];

void init() {
  string s[2];
  cin >> s[0] >> s[1];
  int l[2];
  l[0] = s[0].length();
  l[1] = s[1].length();
  reps(i, 1, l[0] + 1) {
    reps(j, 1, l[1] + 1) {
      if (s[0][i - 1] == s[1][j - 1]) {
        dp[i][j] = dp[i - 1][j - 1] + 1;
      } else {
        dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
      }
    }
  }
  string res = "";
  int jma = l[1] + 1;
  rreps(i, l[0] + 1, 1) {
    rreps(j, jma, 1) {
      if (dp[i - 1][j - 1] + 1 == dp[i][j] && dp[i - 1][j] + 1 == dp[i][j] &&
          dp[i][j - 1] + 1 == dp[i][j]) {
        res += s[0][i - 1];
        break;
      }
    }
  }
  assert(res.length() == dp[l[0]][l[1]]);
  reverse(all(res));
  cout << res << endl;
}

void solve() {}


Fixed submission:
#include "bits/stdc++.h"

using ll = long long;

using namespace std;

// 0 -> a-1
#define rep(i, a) for (int i = 0; (i) < (int)(a); (i)++)
// a -> b-1
#define reps(i, a, b) for (int i = (int)(a); (i) < (int)(b); (i)++)
// a-1 -> 0
#define rrep(i, a) for (int i = (int)a - 1; (i) >= 0; (i)--)
// a-1 -> b
#define rreps(i, a, b) for (int i = (int)(a)-1; (i) >= (int)(b); (i)--)
#define MP(a, b) make_pair((a), (b))
#define PB(a) push_back((a))
#define all(v) (v).begin(), (v).end()
// next_permutation(all(v))
#define PERM(v) next_permutation(all(v))
/*sort(all(v));
(v).erase(unique(all(v)), v.end())*/
#define UNIQUE(v)                                                              \
  sort(all(v));                                                                \
  (v).erase(unique(all(v)), v.end())
#define CIN(type, x)                                                           \
  type x;                                                                      \
  cin >> x
#define YES(f)                                                                 \
  if ((f)) {                                                                   \
    cout << "YES" << endl;                                                     \
  } else {                                                                     \
    cout << "NO" << endl;                                                      \
  }
#define Yes(f)                                                                 \
  if ((f)) {                                                                   \
    cout << "Yes" << endl;                                                     \
  } else {                                                                     \
    cout << "No" << endl;                                                      \
  }
#define MINV(v) min_element(all(v))
#define MAXV(v) max_element(all(v))
#define MIN3(a, b, c) min(min(a, b), c)
#define MIN4(a, b, c, d) min(MIN3(a, b, c), d)
#define MIN5(a, b, c, d, e) min(MIN4(a, b, c, d), e)
#define MIN6(a, b, c, d, e, f) min(MIN5(a, b, c, d, e), f)
#define MAX3(a, b, c) max(max(a, b), c)
#define MAX4(a, b, c, d) max(MAX3(a, b, c), d)
#define MAX5(a, b, c, d, e) max(MAX4(a, b, c, d), e)
#define MAX6(a, b, c, d, e, f) max(MAX5(a, b, c, d, e), f)
// b is [a, c)
#define RANGE(a, b, c) ((a) <= (b) && (b) < (c))
// c is [a, e) && d is [b, f)
#define RANGE2D(a, b, c, d, e, f) (RANGE((a), (c), (e)) && RANGE((b), (d), (f)))
#define chmin(a, b) a = min(a, (b))
#define chmin3(a, b, c) a = MIN3(a, (b), (c))
#define chmin4(a, b, c, d) a = MIN4(a, (b), (c), (d))
#define chmin5(a, b, c, d, e) a = MIN5(a, (b), (c), (d), (e))
#define chmin6(a, b, c, d, e, f) a = MIN6(a, (b), (c), (d), (e), (f))
#define chmax(a, b) a = max(a, (b))
#define chmax3(a, b, c) a = MAX3(a, (b), (c))
#define chmax4(a, b, c, d) a = MAX4(a, (b), (c), (d))
#define chmax5(a, b, c, d, e) a = MAX5(a, (b), (c), (d), (e))
#define chmax6(a, b, c, d, e, f) a = MAX6(a, (b), (c), (d), (e), (f))
#define fcout cout << fixed << setprecision(12)
#define RS resize
#define CINV(v, N)                                                             \
  do {                                                                         \
    v.RS(N);                                                                   \
    rep(i, N) cin >> v[i];                                                     \
  } while (0);

#define RCINV(v, N)                                                            \
  do {                                                                         \
    v.RS(N);                                                                   \
    rrep(i, N) cin >> v[i];                                                    \
  } while (0);
#define MOD 1000000007

template <class T> inline T GET() {
  T x;
  cin >> x;
  return x;
}

void init();
void solve();

signed main() {
  init();
  solve();
}

int dp[3123][3123];

void init() {
  string s[2];
  cin >> s[0] >> s[1];
  int l[2];
  l[0] = s[0].length();
  l[1] = s[1].length();
  reps(i, 1, l[0] + 1) {
    reps(j, 1, l[1] + 1) {
      if (s[0][i - 1] == s[1][j - 1]) {
        dp[i][j] = dp[i - 1][j - 1] + 1;
      } else {
        dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
      }
    }
  }
  string res = "";
  int jma = l[1] + 1;
  rreps(i, l[0] + 1, 1) {
    rreps(j, jma, 1) {
      if (dp[i - 1][j - 1] + 1 == dp[i][j] && dp[i - 1][j] + 1 == dp[i][j] &&
          dp[i][j - 1] + 1 == dp[i][j]) {
        res += s[0][i - 1];
        jma = j;
        break;
      } else if (dp[i][j - 1] + 1 == dp[i][j]) {
        break;
      }
    }
  }
  assert(res.length() == dp[l[0]][l[1]]);
  reverse(all(res));
  cout << res << endl;
}

void solve() {}