Submission #944321

#	Time	Username	Problem	Language	Result	Execution time	Memory
944321		fzyzzz_z	Palindromic Partitions (CEOI17_palindromic)	C++17	100 / 100	750 ms	52124 KiB

palindromic

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

using ll = long long; 

const ll inf = 1e18 + 50;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
struct hashBasic {
    const long long M = 1e9 + 7; 
    const long long B = uniform_int_distribution<long long>(0, M - 1)(rng);
    vector<long long> mpow, hash; 
    long long mul(long long a, long long b) {
        __int128 x = (__int128)a * b; return x % M; 
        return (a * b) % M; 
    }

    hashBasic(string s) {
        hash = vector<long long> (s.size() + 1); 
        mpow.push_back(1); hash[0] = 0; 
        while (mpow.size() < s.size()) {
            mpow.push_back(mul(mpow.back(), B)); }
        for (int i = 0; i < s.size(); ++i) {
            hash[i+1] = (mul(hash[i], B) + s[i]) % M; }
    } 
    
    long long get(int l, int r) { //on [l, r]
        r++; 
        long long ret = hash[r] - mul(hash[l], mpow[r - l]); 
        return (ret + M) % M; 
    }
}; 

void solve() {
    string s; 
    cin >> s; 
    int n = (int) s.size(); 
    hashBasic h1(s), h2(s); 

    int ans = 0; 
    int l = 0, r = n - 1, l0 = -1, r0 = n; 
    while (l < r) {
        if (h1.get(l0 + 1, l) == h1.get(r, r0 - 1) && h2.get(l0 + 1, l) == h2.get(r, r0 - 1)) {
            ans += 2; 
            l0 = l; 
            r0 = r; 
        }
        l++; 
        r--; 
    }
    if (l0 + 1 < r0) ans++; 

    cout << ans << "\n";
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int t; 
    cin >> t; 
    while (t--) {
        solve(); 
    }

    return 0;
}

Compilation message (stderr)

palindromic.cpp: In constructor 'hashBasic::hashBasic(std::string)':
palindromic.cpp:23:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   23 |         for (int i = 0; i < s.size(); ++i) {
      |                         ~~^~~~~~~~~~

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