oj.uz

Submission #1097780

# Submission time Handle Problem Language Result Execution time Memory
1097780 2024-10-08T09:16:40 Z duckindog Palindromes (APIO14_palindrome) C++17
100 / 100
 724 ms 36268 KB 
#include <bits/stdc++.h>

using namespace std;

const int N = 300'000 + 10;
string s;
int n;

struct Hash { 
  int base, M;
  vector<int> h, rh, pw;
  Hash() : base(0), M(0) {}
  Hash(string s, int base, int M) : base(base), M(M), h(s.size() + 1), rh(s.size() + 1), pw(s.size() + 1) { 
    pw[0] = 1;
    for (int i = 1; i <= n; ++i) { 
      pw[i] = 1ll * pw[i - 1] * base % M;
      h[i] = (1ll * h[i - 1] * base % M + s[i - 1]) % M;
      rh[i] = (1ll * rh[i - 1] * base % M + s[n - i]) % M;
    }
  }

  int get(int l, int r) { 
    return (h[r] - 1ll * h[l - 1] * pw[r - l + 1] % M + M) % M; 
  }
  int rget(int l, int r) { 
    return (rh[r] - 1ll * rh[l - 1] * pw[r - l + 1] % M + M) % M; 
  }
} T[2];

using HASH = pair<int, int>;
inline HASH get(int l, int r) { 
  return make_pair(T[0].get(l, r), T[1].get(l, r));
}
inline HASH rget(int l, int r) { 
  tie(l, r) = make_pair(n - r + 1, n - l + 1);
  return make_pair(T[0].rget(l, r), T[1].rget(l, r));
}
inline bool chk(int l, int r) { return get(l, r) == rget(l, r); }

int pos[N], tmp[N], sa[N];
int lcp[N];

void initSA() { 
  for (int i = 1; i <= n; ++i) pos[i] = s[i] - 'a' + 1, sa[i] = i;
  for (int gap = 1; ; gap *= 2) { 
    auto cmp = [&](int i, int j) { 
      if (pos[i] != pos[j]) return pos[i] < pos[j];
      i += gap; j += gap;
      return i <= n && j <= n ? pos[i] < pos[j] : i > j;
    };
    
    sort(sa + 1, sa + n + 1, cmp);
    for (int i = 2; i <= n; ++i) tmp[i] = tmp[i - 1] + cmp(sa[i - 1], sa[i]);
    for (int i = 1; i <= n; ++i) pos[sa[i]] = tmp[i] + 1;
    if (tmp[n] == n - 1) break;
  }
  
  for (int i = 1, k = 0; i <= n; ++i) { 
    if (pos[i] == n) continue;
    for (int j = sa[pos[i] + 1]; s[i + k] == s[j + k]; ) k += 1;
    lcp[i] = k;
    if (k) k -= 1;
  }
}

int f[N][19], lg[N];
void init() { 
  for (int i = 2; i <= n; ++i) lg[i] = lg[i >> 1] + 1;
  for (int i = 1; i <= n; ++i) f[i][0] = lcp[sa[i]];
  for (int j = 1; j <= 18; ++j) { 
    for (int i = 1; i <= n - (1 << j) + 1; ++i)
      f[i][j] = min(f[i][j - 1], f[i + (1 << j - 1)][j - 1]);
  }
}
inline int que(int l, int r) { 
  int j = lg[r - l + 1];
  return min(f[l][j], f[r - (1 << j) + 1][j]);
}

int32_t main() { 
  cin.tie(0)->sync_with_stdio(0);

  cin >> s;
  n = s.size();
  
  T[0] = Hash(s, 19937, 1e9 + 7);
  T[1] = Hash(s, 10007, 1e9 + 9);
  
  s = '@' + s;
  initSA();
  init();
  
  auto count = [&](int l, int r) { 
    int sz = r - l + 1;
    l = pos[l];
    int value = 0;
    { // binarySearch left
      int le = 1, ri = l - 1, ret = l;
      while (le <= ri) { 
        int mid = (le + ri) >> 1;
        if (que(mid, l - 1) >= sz) ri = (ret = mid) - 1;
        else le = mid + 1;
      }
      
      value -= ret - 1;
    }

    { //binarySearch right
      int le = l, ri = n - 1, ret = l;
      while (le <= ri) { 
        int mid = (le + ri) >> 1;
        if (que(l, mid) >= sz) le = ret = mid + 1;
        else ri = mid - 1;
      }

      value += ret;
    }
    return value;
  };
  
  long long answer = 0;
  for (int mid1 = 1; mid1 <= n; ++mid1) { 
    for (int mid2 = mid1; mid2 <= min(n, mid1 + 1); ++mid2) { 
      if (!chk(mid1, mid2)) continue;
      
      int sz = min(mid1, n - mid2);
      int l = 0, r = sz, ret = 0;
      while (l <= r) { 
        int mid = (l + r) >> 1;

        if (chk(mid1 - mid, mid2 + mid)) l = (ret = mid) + 1;
        else r = mid - 1;
      }
      
      answer = max(answer, 1ll * count(mid1 - ret, mid2 + ret) * (mid2 - mid1 + 2 * ret + 1));
    }
  }
  
  cout << answer << "\n";
}

Compilation message

palindrome.cpp: In function 'void init()':
palindrome.cpp:72:48: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
   72 |       f[i][j] = min(f[i][j - 1], f[i + (1 << j - 1)][j - 1]);
      |                                              ~~^~~

Subtask #1
8.0 / 8.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 344 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 0 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 0 ms 348 KB Output is correct
6 Correct 0 ms 348 KB Output is correct
7 Correct 0 ms 348 KB Output is correct
8 Correct 0 ms 348 KB Output is correct
9 Correct 0 ms 348 KB Output is correct
10 Correct 0 ms 348 KB Output is correct
11 Correct 0 ms 348 KB Output is correct
12 Correct 0 ms 348 KB Output is correct
13 Correct 1 ms 344 KB Output is correct
14 Correct 0 ms 348 KB Output is correct
15 Correct 0 ms 348 KB Output is correct
16 Correct 1 ms 348 KB Output is correct
17 Correct 0 ms 348 KB Output is correct
18 Correct 0 ms 348 KB Output is correct
19 Correct 0 ms 348 KB Output is correct
20 Correct 1 ms 344 KB Output is correct
21 Correct 0 ms 348 KB Output is correct
22 Correct 0 ms 348 KB Output is correct
23 Correct 0 ms 348 KB Output is correct
24 Correct 0 ms 348 KB Output is correct
25 Correct 1 ms 348 KB Output is correct
26 Correct 0 ms 348 KB Output is correct
27 Correct 0 ms 348 KB Output is correct
28 Correct 0 ms 348 KB Output is correct
29 Correct 1 ms 348 KB Output is correct
30 Correct 0 ms 348 KB Output is correct
31 Correct 0 ms 348 KB Output is correct
32 Correct 0 ms 348 KB Output is correct

Subtask #2
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 604 KB Output is correct
2 Correct 1 ms 604 KB Output is correct
3 Correct 1 ms 604 KB Output is correct
4 Correct 1 ms 604 KB Output is correct
5 Correct 1 ms 604 KB Output is correct
6 Correct 1 ms 604 KB Output is correct
7 Correct 1 ms 604 KB Output is correct
8 Correct 1 ms 604 KB Output is correct
9 Correct 1 ms 600 KB Output is correct
10 Correct 1 ms 600 KB Output is correct
11 Correct 1 ms 604 KB Output is correct
12 Correct 1 ms 524 KB Output is correct

Subtask #3
24.0 / 24.0

# Verdict Execution time Memory Grader output
1 Correct 8 ms 1628 KB Output is correct
2 Correct 8 ms 1628 KB Output is correct
3 Correct 12 ms 1716 KB Output is correct
4 Correct 11 ms 1628 KB Output is correct
5 Correct 9 ms 1628 KB Output is correct
6 Correct 9 ms 1628 KB Output is correct
7 Correct 8 ms 1536 KB Output is correct
8 Correct 6 ms 1604 KB Output is correct
9 Correct 6 ms 1716 KB Output is correct
10 Correct 10 ms 1628 KB Output is correct

Subtask #4
26.0 / 26.0

# Verdict Execution time Memory Grader output
1 Correct 105 ms 12556 KB Output is correct
2 Correct 100 ms 12364 KB Output is correct
3 Correct 146 ms 12368 KB Output is correct
4 Correct 134 ms 12536 KB Output is correct
5 Correct 161 ms 12368 KB Output is correct
6 Correct 134 ms 12536 KB Output is correct
7 Correct 122 ms 12368 KB Output is correct
8 Correct 98 ms 12532 KB Output is correct
9 Correct 119 ms 12560 KB Output is correct
10 Correct 169 ms 12528 KB Output is correct

Subtask #5
27.0 / 27.0

# Verdict Execution time Memory Grader output
1 Correct 369 ms 36184 KB Output is correct
2 Correct 348 ms 36236 KB Output is correct
3 Correct 495 ms 36228 KB Output is correct
4 Correct 463 ms 36192 KB Output is correct
5 Correct 642 ms 36232 KB Output is correct
6 Correct 426 ms 36228 KB Output is correct
7 Correct 448 ms 36268 KB Output is correct
8 Correct 353 ms 36044 KB Output is correct
9 Correct 353 ms 36228 KB Output is correct
10 Correct 724 ms 36232 KB Output is correct
11 Correct 364 ms 36232 KB Output is correct
12 Correct 446 ms 36232 KB Output is correct