oj.uz

Submission #617101

# Submission time Handle Problem Language Result Execution time Memory
617101 2022-08-01T08:42:27 Z juancarlovieri Palinilap (COI16_palinilap) C++17
100 / 100
 89 ms 24888 KB 
#include <bits/stdc++.h>
using namespace std;

#define int long long
#define mod 1000000007

mt19937 gen(33);
uniform_int_distribution<> rd(1, 1000000000);
int pre[100005];
int prer[100005];
int pw[100005];
int p;
int all[100005][26];
int n;

int take(int l, int r) {
  int res = pre[r];
  if (l) {
    res -= pw[r - l + 1] * pre[l - 1] % mod;
  }
  res += mod;
  res %= mod;
  return res;
}

int takerev(int l, int r) {
  int res = prer[r];
  if (r) {
    res -= pw[r - l + 1] * prer[l - 1] % mod;
  }
  res += mod;
  res %= mod;
  return res;
}

bool eq(int a, int b, int c, int d) {
  return take(a, b) == takerev(n - d - 1, n - c - 1);
}

signed main() {
  p = rd(gen);
  string s;
  cin >> s;
  n = s.length();
  auto srev = s;
  reverse(srev.begin(), srev.end());
  pw[0] = 1;
  for (int i = 1; i < n; ++i) pw[i] = pw[i - 1] * p % mod;
  pre[0] = s[0] % mod;
  for (int i = 1; i < n; ++i) {
    pre[i] = (pre[i - 1] * p % mod + s[i]) % mod;
  }
  prer[0] = srev[0] % mod;
  for (int i = 1; i < n; ++i) {
    prer[i] = (prer[i - 1] * p % mod + srev[i]) % mod;
  }
  int act = 0;
  vector<pair<int, int>> diff(n + 5);
  // cout << pw[2] << endl;
  // cout << take(0, 1) <<  ' ' << take(2, 3) << endl;

  for (int i = 0; i < n; ++i) {
    for (int j = i; j <= i + 1; ++j) {
      if (j >= n) continue;
      int lo = 0, hi = min(i, n - j - 1);
      while (lo <= hi) {
        int mid = (lo + hi) / 2;
        if (eq(i - mid, i, j, j + mid)) {
        // if (take(i - mid, i) == take(j, j + mid)) {
          lo = mid + 1;
        } else hi = mid - 1;
      }
      if (hi >= 0) {
        // assert(take(i - hi, i) == take(j, j + hi)); 
      }
      // cout << "hi" << hi << ' ' << take(0, 1) << ' ' << takerev(0, 1) << endl;
      act += hi + 1;
      if (i == j) {
        diff[j + 1].first += -1;
        diff[j + hi + 1].first -= - 1;
        diff[j + 1].second += j + hi + 1;
        diff[j + hi + 1].second -= j + hi + 1;

        diff[i - (hi + 1) + 1].first += 1;
        diff[i].first -= 1;
        diff[i - (hi + 1) + 1].second += -(i - (hi + 1));
        diff[i].second -= -(i - (hi + 1));
      } else {
        diff[j].first += -1;
        diff[j + hi + 1].first -= - 1;
        diff[j].second += j + hi + 1;
        diff[j + hi + 1].second -= j + hi + 1;

        diff[i - (hi + 1) + 1].first += 1;
        diff[i + 1].first -= 1;
        diff[i - (hi + 1) + 1].second += -(i - (hi + 1));
        diff[i + 1].second -= -(i - (hi + 1));
      }

      int x = i - hi - 1;
      int y = j + hi + 1;
      if (x < 0 or y > n - 1) continue;
      lo = 1, hi = min(x, n - y - 1);
      while (lo <= hi) {
        int mid = (lo + hi) / 2;
        if (eq(x - mid, x - 1, y + 1, y + mid)) {
        // if (take(x - mid, x - 1) == take(y + 1, y + mid)) {
          lo = mid + 1;
        } else hi = mid - 1;
      }
      if (hi > 0) {
        // assert(take(x - hi, x - 1) == take(y + 1, y + hi));
      }
      // if (i == 0 and j == 1) cout << x << ' ' << y << ' ' << hi + 1 << endl;
      all[x][s[y] - 'a'] += hi + 1;
      all[y][s[x] - 'a'] += hi + 1;
    }
  }
  int ans = act;
  int cur = act;
  // cout << cur << endl;
  int delta = 0;
  int m = 0, c=  0;
  for (int i = 0; i < n; ++i) {
    // delta += diff[i];
    // cur += delta;
    m += diff[i].first;
    c += diff[i].second;
    // cout << delta << endl; 
    for (int j = 0; j < 26; ++j) {
      if ((s[i] - 'a') == j) continue;
      // cout << all[i][j] << ' ';
      // if (i == 1 and j == 2) cout << "INI " << all[i][j] << endl;
      ans = max(ans, cur + all[i][j] - (i * m + c));
      // if (i == 1 and j == 0) cout << cur << endl;
      // cout << i << ' ' << j << ' ' << cur + all[i][j] + 1 << endl;
    }
    // cout << endl;
    // cout << cur << ' ';
  }
  // cout << endl;
  cout << ans << endl;
  // delta += diff[n];
  // cur += delta;
  assert(cur == act);
  // cout << cur << endl;
}

Compilation message

palinilap.cpp: In function 'int main()':
palinilap.cpp:122:7: warning: unused variable 'delta' [-Wunused-variable]
  122 |   int delta = 0;
      |       ^~~~~

Subtask #1
17.0 / 17.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 340 KB Output is correct
2 Correct 1 ms 340 KB Output is correct
3 Correct 1 ms 340 KB Output is correct
4 Correct 0 ms 340 KB Output is correct
5 Correct 0 ms 340 KB Output is correct

Subtask #2
37.0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 1620 KB Output is correct
2 Correct 2 ms 1492 KB Output is correct
3 Correct 4 ms 1492 KB Output is correct
4 Correct 3 ms 1052 KB Output is correct
5 Correct 3 ms 1364 KB Output is correct
6 Correct 3 ms 1480 KB Output is correct
7 Correct 3 ms 1512 KB Output is correct

Subtask #3
46.0 / 46.0

# Verdict Execution time Memory Grader output
1 Correct 71 ms 24680 KB Output is correct
2 Correct 63 ms 24884 KB Output is correct
3 Correct 55 ms 24856 KB Output is correct
4 Correct 78 ms 24796 KB Output is correct
5 Correct 75 ms 24840 KB Output is correct
6 Correct 66 ms 24888 KB Output is correct
7 Correct 88 ms 24776 KB Output is correct
8 Correct 39 ms 4564 KB Output is correct
9 Correct 70 ms 24808 KB Output is correct
10 Correct 78 ms 24840 KB Output is correct
11 Correct 49 ms 24780 KB Output is correct
12 Correct 89 ms 24856 KB Output is correct
13 Correct 82 ms 24888 KB Output is correct
14 Correct 86 ms 24868 KB Output is correct
15 Correct 83 ms 24788 KB Output is correct
16 Correct 69 ms 24832 KB Output is correct
17 Correct 73 ms 24772 KB Output is correct
18 Correct 79 ms 24836 KB Output is correct
19 Correct 84 ms 24828 KB Output is correct