Submission #856377

#	Time	Username	Problem	Language	Result	Execution time	Memory
856377		Cyanmond	Palindromic Partitions (CEOI17_palindromic)	C++17	100 / 100	341 ms	23940 KiB

palindromic

#include <bits/stdc++.h>

using namespace std;

#define rep(i, l, r) for (int i = (l); i < (r); ++i)
#define per(i, l, r) for (int i = (r - 1); i >= l; --i)
#define ALL(x) (x).begin(), (x).end()

using i64 = long long;

using u64 = unsigned long long;
constexpr u64 mod = (1ull << 61) - 1;
constexpr u64 base = 121907;

u64 safeMod(__uint128_t v) {
    return v % mod;
}

struct SH {
    static u64 mul(u64 a, u64 b) {
        __uint128_t x = (__uint128_t)(a) * (__uint128_t)(b);
        return safeMod(x % (__uint128_t)mod);
    }

    int n;
    string S;
    vector<u64> hash;

    SH(string s) : S(s) {
        n = (int)S.size();
        hash.assign(n + 1, 0);
        rep(i, 0, n) {
            hash[i + 1] = safeMod(mul(hash[i], base) + (u64)(S[i]));
        }
    }
};

void main_() {
    string S;
    cin >> S;
    const int N = (int)S.size();
    string A = S.substr(0, N / 2), B = S.substr(N - N / 2, N / 2);
    const int M = (int)A.size();
    vector<u64> baseTable(M + 10);
    baseTable[0] = 1;
    rep(i, 1, M + 10) baseTable[i] = SH::mul(baseTable[i - 1], base);

    SH ha(A), hb(B);

    auto judge = [&](int l, int r) {
        u64 hs1 = safeMod(ha.hash[r] + mod - SH::mul(ha.hash[l], baseTable[r - l]));
        u64 hs2 = safeMod(hb.hash[M - l] + mod - SH::mul(hb.hash[M - r], baseTable[r - l]));
        return hs1 == hs2;
    };

    int l = 0, r = 0;
    int ans = 0;
    while (l != M) {
        while (r != M) {
            ++r;
            if (judge(l, r)) {
                break;
            }
        }
        if (not judge(l, r)) {
            ++ans;
            break;
        }
        ans += 2;
        l = r;
        if (l == M) {
            if (N % 2 == 1) ++ans;
            break;
        }
    }
    if (N == 1) ++ans;
    cout << ans << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int T;
    cin >> T;
    while (T--) main_();
}

• Subtask 1: 15 / 15
• Subtask 2: 20 / 20
• Subtask 3: 25 / 25
• Subtask 4: 40 / 40