Problem p02913 (C++)

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

#ifdef LOCAL
#include "../../dump.hpp"
#else
#define dump(...)
#endif

#define int ll
#define rep(i, n) for (int i = 0, i##_cond = (n); i < i##_cond; ++i)
#define FOR(i, a, b) for (int i = (a), i##_cond = (b); i < i##_cond; ++i)
#define ROF(i, a, b)                                                           \
  for (int i = (a)-1, i##_cond = (b); i >= i##_cond; --i) // ROF(i,n,0)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend() // sortで降順
#define SUM(a) accumulate(all(a), int(0))
using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vs = vector<string>;
using pii = pair<int, int>;
constexpr ll inf = 1ll << 61;
constexpr ll mod = 1e9 + 7;
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> T add(const T &a, const T &b) { return (a + b) % mod; }

template <unsigned mod> struct RollingHash {
  vector<unsigned> hashed, power;

  inline unsigned mul(unsigned a, unsigned b) const {
    unsigned long long x = (unsigned long long)a * b;
    unsigned xh = (unsigned)(x >> 32), xl = (unsigned)x, d, m;
    asm("divl %4; \n\t" : "=a"(d), "=d"(m) : "d"(xh), "a"(xl), "r"(mod));
    return m;
  }

  RollingHash(const string &s, unsigned base = 10007) {
    int sz = (int)s.size();
    hashed.assign(sz + 1, 0);
    power.assign(sz + 1, 0);
    power[0] = 1;
    for (int i = 0; i < sz; i++) {
      power[i + 1] = mul(power[i], base);
      hashed[i + 1] = mul(hashed[i], base) + s[i];
      if (hashed[i + 1] >= mod)
        hashed[i + 1] -= mod;
    }
  }

  unsigned get(int l, int r) const {
    unsigned ret = hashed[r] + mod - mul(hashed[l], power[r - l]);
    if (ret >= mod)
      ret -= mod;
    return ret;
  }

  unsigned connect(unsigned h1, int h2, int h2len) const {
    unsigned ret = mul(h1, power[h2len]) + h2;
    if (ret >= mod)
      ret -= mod;
    return ret;
  }

  int LCP(const RollingHash<mod> &b, int l1, int r1, int l2, int r2) {
    int len = min(r1 - l1, r2 - l2);
    int low = -1, high = len + 1;
    while (high - low > 1) {
      int mid = (low + high) / 2;
      if (get(l1, l1 + mid) == b.get(l2, l2 + mid))
        low = mid;
      else
        high = mid;
    }
    return (low);
  }
};

using RH = RollingHash<1000000007>;

signed main() {
  int n;
  cin >> n;
  string s;
  cin >> s;

  RH rh(s);
  int ans = 0;
  rep(i, n) FOR(j, i + 1, n) { // i : 左, j : 右
    int ok = 0;
    int ng = n;
    while (abs(ok - ng) > 1) {
      int mid = (ok + ng) / 2; // 文字数

      bool f;
      if (i + mid <= j and j + mid <= n) {
        if (rh.get(i, i + mid - 1) == rh.get(j, j + mid - 1) and
            s.substr(i, mid) == s.substr(j, mid))
          f = true;
        else
          f = false;
      } else {
        f = false;
      }

      if (f) {
        ok = mid;
      } else {
        ng = mid;
      }
    }
    chmax(ans, ok);
  }
  cout << ans << endl;
}


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

#ifdef LOCAL
#include "../../dump.hpp"
#else
#define dump(...)
#endif

#define int ll
#define rep(i, n) for (int i = 0, i##_cond = (n); i < i##_cond; ++i)
#define FOR(i, a, b) for (int i = (a), i##_cond = (b); i < i##_cond; ++i)
#define ROF(i, a, b)                                                           \
  for (int i = (a)-1, i##_cond = (b); i >= i##_cond; --i) // ROF(i,n,0)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend() // sortで降順
#define SUM(a) accumulate(all(a), int(0))
using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vs = vector<string>;
using pii = pair<int, int>;
constexpr ll inf = 1ll << 61;
constexpr ll mod = 1e9 + 7;
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> T add(const T &a, const T &b) { return (a + b) % mod; }

template <unsigned mod> struct RollingHash {
  vector<unsigned> hashed, power;

  inline unsigned mul(unsigned a, unsigned b) const {
    unsigned long long x = (unsigned long long)a * b;
    unsigned xh = (unsigned)(x >> 32), xl = (unsigned)x, d, m;
    asm("divl %4; \n\t" : "=a"(d), "=d"(m) : "d"(xh), "a"(xl), "r"(mod));
    return m;
  }

  RollingHash(const string &s, unsigned base = 10007) {
    int sz = (int)s.size();
    hashed.assign(sz + 1, 0);
    power.assign(sz + 1, 0);
    power[0] = 1;
    for (int i = 0; i < sz; i++) {
      power[i + 1] = mul(power[i], base);
      hashed[i + 1] = mul(hashed[i], base) + s[i];
      if (hashed[i + 1] >= mod)
        hashed[i + 1] -= mod;
    }
  }

  unsigned get(int l, int r) const {
    unsigned ret = hashed[r] + mod - mul(hashed[l], power[r - l]);
    if (ret >= mod)
      ret -= mod;
    return ret;
  }

  unsigned connect(unsigned h1, int h2, int h2len) const {
    unsigned ret = mul(h1, power[h2len]) + h2;
    if (ret >= mod)
      ret -= mod;
    return ret;
  }

  int LCP(const RollingHash<mod> &b, int l1, int r1, int l2, int r2) {
    int len = min(r1 - l1, r2 - l2);
    int low = -1, high = len + 1;
    while (high - low > 1) {
      int mid = (low + high) / 2;
      if (get(l1, l1 + mid) == b.get(l2, l2 + mid))
        low = mid;
      else
        high = mid;
    }
    return (low);
  }
};

using RH = RollingHash<1000000007>;

signed main() {
  int n;
  cin >> n;
  string s;
  cin >> s;

  RH rh(s);
  int ans = 0;
  rep(i, n) FOR(j, i + 1, n) { // i : 左, j : 右
    int ok = 0;
    int ng = n;
    while (abs(ok - ng) > 1) {
      int mid = (ok + ng) / 2; // 文字数

      bool f;
      if (i + mid <= j and j + mid <= n) {
        if (rh.get(i, i + mid) == rh.get(j, j + mid))
          f = true;
        else
          f = false;
      } else {
        f = false;
      }

      if (f) {
        ok = mid;
      } else {
        ng = mid;
      }
    }
    chmax(ans, ok);
  }
  cout << ans << endl;
}