Submission #617101

#TimeUsernameProblemLanguageResultExecution timeMemory
617101juancarlovieriPalinilap (COI16_palinilap)C++17
100 / 100
89 ms24888 KiB
#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 (stderr)

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