Submission #1097275

#	Time	Username	Problem	Language	Result	Execution time	Memory
1097275		vjudge1	Palindromic Partitions (CEOI17_palindromic)	C++17	0 / 100	1 ms	348 KiB

palindromic

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mod = 1e9 + 7;
const int p = 41;

int binpow(int a,int b){
    if(!b)return 1;
    int res = binpow(a,b/2);
    res = (res * res) % mod;
    if(b&1)res = (res * a) % mod;
    return res;
}

void solve(){
    string s;
    cin >> s;
    int n = s.size();
    s = "." + s;
    vector<int> pi(n+1,1),res(n+1,0);
    for(int i=1;i<=n;++i){
        pi[i] = pi[i-1] * p % mod;
        res[i] = res[i-1] + ((pi[i] * (s[i] - 'a' + 1)) % mod);
        res[i] %= mod;
    }
    int l=0,r=n;
    int cnt = 1;
    int ind = (n&1 ? n/2 + 1 : n/2);
    for(int i=1;i<=n/2;++i){
        int a = (res[i] - res[l] + mod) % mod;
        a *= (l == 0 ? 1 : binpow(pi[l],mod-2));
        a %= mod;
        int b = (res[r] - res[r - (i - l)] + mod) % mod;
        b *= binpow(pi[r - (i - l)],mod-2);
        b %= mod;
        // cout << a << ' ' << b << '\n';
        if(a == b){
            l = i;
            r = n-l;
            cnt += 2;
        }
    }
    cout << cnt;
}

signed main(){
    int t;
    cin >> t;
    for(int tt=0;tt<t;++tt){
        solve();
        cout << '\n';
    }
}

Compilation message (stderr)

palindromic.cpp: In function 'void solve()':
palindromic.cpp:28:9: warning: unused variable 'ind' [-Wunused-variable]
   28 |     int ind = (n&1 ? n/2 + 1 : n/2);
      |         ^~~

• Subtask 1: 0 / 15
• Subtask 2: 0 / 20
• Subtask 3: 0 / 25
• Subtask 4: 0 / 40