제출 #1106401

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1106401		_callmelucian	Palinilap (COI16_palinilap)	C++14	100 / 100	723 ms	39252 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 + 7;
const ll base = 21121;

int add (int a, int b) { return a + b - (a + b < MOD ? 0 : MOD); }

int sub (int a, int b) { return a - b + (a - b >= 0 ? 0 : MOD); }

int mul (int a, int b) { return 1LL * a * b % MOD; }

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

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

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

    void update (int k, int delta) {
        if (delta < 0) delta += MOD;
        for (int t = 0; k < tr.size(); t += p(k), k += p(k))
            tr[k] = add(tr[k], mul(delta, basePow[t]));
    }

    int preSum (int k) {
        int ans = 0;
        for (int t = 0; k; t += p(k), k -= p(k))
            ans = add(ans, mul(tr[k], basePow[t]));
        return ans;
    }

    int query (int l, int r) {
        return sub(preSum(r), mul(preSum(l - 1), basePow[r - l + 1]));
    }
} preHash(mn), sfxHash(mn);

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

bool valid (int l, int r) {
    if (l < 1 || r > n) return 0;
    if (l == r) return 1;
    return preHash.query(l, r) == sfxHash.query(rev(r), rev(l));
}

bool checkOdd (int core, int wing) {
    return valid(core - wing + 1, core + wing - 1);
}

bool checkEven (int core, int wing) {
    return valid(core - wing + 1, core + wing);
}

int calcOdd (int i) {
    int wingOdd = 0;
    for (int msk = 1 << 15; msk > 0; msk >>= 1)
        if (checkOdd(i, wingOdd | msk)) wingOdd |= msk;
    return wingOdd;
}

int calcEven (int i) {
    int wingEven = 0;
    for (int msk = 1 << 15; msk > 0; msk >>= 1)
        if (checkEven(i, wingEven | msk)) wingEven |= msk;
    return wingEven;
}

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

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;
    for (int i = 1; i <= n; i++) {
        int wingOdd = calcOdd(i), wingEven = calcEven(i);
        curAns += wingOdd + wingEven;

        //cout << "dbg " << i << " " << wingOdd << " " << wingEven << "\n";

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

        if (wingOdd > 1) {
            // disturb odd palindrome
            open[i - wingOdd + 1].emplace_back(i - wingOdd, 1), close[i - 1].emplace_back(i - wingOdd, 1);
            open[i + 1].emplace_back(i + wingOdd, 0), close[i + wingOdd - 1].emplace_back(i + wingOdd, 0);
        }
        if (wingEven > 0) {
            // disturb even palindrome
            open[i - wingEven + 1].emplace_back(i - wingEven, 1), close[i].emplace_back(i - wingEven, 1);
            open[i + 1].emplace_back(i + wingEven + 1, 0), close[i + wingEven].emplace_back(i + wingEven + 1, 0);
        }
    }

    // try changing each letter
    ll ans = curAns, sumLeft = 0, cntLeft = 0, sumRight = 0, cntRight = 0;
    for (int i = 1; i <= n; i++) {
        for (pii item : open[i]) {
            int p, type; tie(p, type) = item;
            if (type) sumLeft += p, cntLeft++;
            else sumRight += p, cntRight++;
        }

        ll rem = i * cntLeft - sumLeft + sumRight - i * cntRight;
        for (int j = 0; j < 26; j++)
            if (j != s[i] - 'a') ans = max(ans, curAns - rem + change[i][j]);

        for (pii item : close[i]) {
            int p, type; tie(p, type) = item;
            if (type) sumLeft -= p, cntLeft--;
            else sumRight -= p, cntRight--;
        }
    }
    cout << ans;

    return 0;
}

컴파일 시 표준 에러 (stderr) 메시지

palinilap.cpp: In member function 'void BIT::update(int, int)':
palinilap.cpp:34:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   34 |         for (int t = 0; k < tr.size(); t += p(k), k += p(k))
      |                         ~~^~~~~~~~~~~

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