Submission #1106343

#	Time	Username	Problem	Language	Result	Execution time	Memory
1106343		_callmelucian	Palinilap (COI16_palinilap)	C++14	0 / 100	1059 ms	32096 KiB

palinilap

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

typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pl;
typedef pair<int,int> pii;
typedef tuple<int,int,int> tt;

#define all(a) a.begin(), a.end()
#define filter(a) a.erase(unique(all(a)), a.end())

const int mn = 1e5 + 5;
const ll MOD = 1e9 + 21;
const ll base = 21121;

ll basePow[mn], conOdd[mn], conEven[mn], change[mn][26];
vector<pii> open[mn], close[mn];
int n;

struct BIT {
    vector<ll> tr;
    BIT (int sz) : tr(sz + 1) {}

    int t (int k) { return k & -k; }

    void update (int k, ll delta) {
        for (int p = 0; k < tr.size(); p += t(k), k += t(k)) {
            ll contrib = delta * basePow[p] % MOD;
            tr[k] = (tr[k] + contrib + MOD) % MOD;
        }
    }

    ll preSum (int k, ll ans = 0) {
        for (int p = 0; k; p += t(k), k -= t(k)) {
            ll contrib = tr[k] * basePow[p] % MOD;
            ans = (ans + contrib) % MOD;
        }
        return ans;
    }

    ll query (int l, int r) {
        return (preSum(r) - preSum(l - 1) * basePow[r - l + 1] + MOD * MOD) % MOD;
    }
} preHash(mn), sfxHash(mn);

int rev (int i) { return n - i + 1; }

bool validOdd (int c, int wing) {
    if (wing == 0) return 1;
    if (c - wing < 1 || c + wing > n) return 0;
    return preHash.query(c - wing, c + wing) == sfxHash.query(rev(c + wing), rev(c - wing));
}

bool validEven (int c, int wing) {
    if (c - wing + 1 < 1 || c + wing > n) return 0;
    return preHash.query(c - wing + 1, c + wing) == sfxHash.query(rev(c + wing), rev(c - wing + 1));
}

void update (int i, int c) {
    preHash.update(i, c), sfxHash.update(rev(i), c);
}

int calcOdd (int i) {
    int ans = 0;
    for (int step = n / 2; step >= 1; step /= 2)
        while (validOdd(i, ans + step)) ans += step;
    return ans;
}

int calcEven (int i) {
    int ans = 0;
    for (int step = n / 2; step >= 1; step /= 2)
        while (validEven(i, ans + step)) ans += step;
    return ans;
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);

    basePow[0] = 1;
    for (int i = 1; i < mn; i++)
        basePow[i] = basePow[i - 1] * base % MOD;

    string s; cin >> s;
    n = s.length(), s = " " + s;

    for (int i = 1; i <= n; i++) update(i, s[i]);

    ll curAns = 0, ans = 0, rem = 0;
    for (int i = 1; i <= n; i++) {
        conOdd[i] = calcOdd(i), conEven[i] = calcEven(i);
        curAns += conOdd[i] + conEven[i];
        int wingOdd = conOdd[i], wingEven = conEven[i];

        // odd-size palindrome
        open[i - wingOdd].emplace_back(i, 1), open[i + 1].emplace_back(i, 1);
        close[i - 1].emplace_back(i, 1), close[i + wingOdd].emplace_back(i, 1);
        // even-size palindrome
        open[i - wingEven + 1].emplace_back(i, 0);
        close[i + wingEven].emplace_back(i, 0);

        if (i - wingOdd - 1 >= 1 && i + wingOdd + 1 <= n) {
            int delta = s[i + wingOdd + 1] - s[i - wingOdd - 1];
            update(i - wingOdd - 1, delta);
            change[i - wingOdd - 1][s[i + wingOdd + 1] - 'a'] += calcOdd(i) - conOdd[i];

            update(i - wingOdd - 1, -delta), update(i + wingOdd + 1, -delta);
            change[i + wingOdd + 1][s[i - wingOdd - 1] - 'a'] += calcOdd(i) - conOdd[i];
            update(i + wingOdd + 1, delta);
        }
        if (i - wingEven >= 1 && i + wingEven + 1 <= n) {
            int delta = s[i + wingEven + 1] - s[i - wingEven];
            update(i - wingEven, delta);
            change[i - wingEven][s[i + wingEven + 1] - 'a'] += calcEven(i) - conEven[i];

            update(i - wingEven, -delta), update(i + wingEven + 1, -delta);
            change[i + wingEven + 1][s[i - wingEven] - 'a'] += calcEven(i) - conEven[i];
            update(i + wingEven + 1, delta);
        }
    }
    ans = curAns;

    for (int i = 1; i <= n; i++) {
        for (pii it : open[i]) {
            int p, odd; tie(p, odd) = it;
            rem += (odd ? conOdd[p] : conEven[p]);
        }

        for (int c = 0; c < 26; c++)
            if (c != s[i] - 'a') ans = max(ans, curAns - rem + change[i][c]);

        for (pii it : close[i]) {
            int p, odd; tie(p, odd) = it;
            rem -= (odd ? conOdd[p] : conEven[p]);
        }
    }
    cout << ans + n;

    return 0;
}

Compilation message (stderr)

palinilap.cpp: In member function 'void BIT::update(int, ll)':
palinilap.cpp:28:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   28 |         for (int p = 0; k < tr.size(); p += t(k), k += t(k)) {
      |                         ~~^~~~~~~~~~~

• Subtask 1: 0 / 17
• Subtask 2: 0 / 37
• Subtask 3: 0 / 46