Submission #744893

#	Time	Username	Problem	Language	Result	Execution time	Memory
744893		zeta7532	Palindromes (APIO14_palindrome)	C++17	0 / 100	1085 ms	88968 KiB

palindrome

#include <bits/stdc++.h>
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
using namespace std;
using ll = long long;
const ll mod = 998244353;
#define fi first
#define se second
#define rep(i,n) for(ll i=0;i<n;i++)
#define all(x) x.begin(),x.end()
#define faster ios::sync_with_stdio(false);cin.tie(nullptr)

ll modpow(ll A,ll N){
    ll res=1;
    while(N){
        if(N&1) res=res*A%mod;
        A=A*A%mod;
        N>>=1;
    }
    return res;
}

ll modinv(ll A){return modpow(A,mod-2);}

int main() {
    string s;
    cin >> s;
    ll N=s.size();
    if(N>10000) return 0;
    vector<ll> A(N+1),B(N+1);
    A[0]=0;
    B[N]=0;
    ll k=1;
    rep(i,N) A[i+1]=(A[i]+(s[i]-'a'+1)*k)%mod,k=k*100%mod;
    k=1;
    for(ll i=N-1;i>=0;i--) B[i]=(B[i+1]+(s[i]-'a'+1)*k)%mod,k=k*100%mod;
    vector<ll> inv(N);
    inv[0]=1;
    rep(i,N-1) inv[i+1]=inv[i]*828542813%mod;
    unordered_map<ll,ll> M;
    ll ans=0;
    for(ll i=0;i<N;i++){
        for(ll j=i;j<N;j++){
            if((A[j+1]-A[i]+mod)*(inv[i])%mod==(B[i]-B[j+1]+mod)*(inv[N-j-1])%mod){
                M[(A[j+1]-A[i]+mod)*(inv[i])%mod]+=j-i+1;
                ans=max(ans,M[(B[i]-B[j+1]+mod)%mod]);
            }    
        }
    }
    cout << ans << endl;
    return 0;
}

• Subtask 1: 0 / 8
• Subtask 2: 0 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 26
• Subtask 5: 0 / 27