Submission #884700

#	Time	Username	Problem	Language	Result	Execution time	Memory
884700		theghostking	Palindromic Partitions (CEOI17_palindromic)	C++17	100 / 100	179 ms	30552 KiB

palindromic

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

#define int long long

const int P = 31;
const int M = 1e9+9;
 
vector<int> binpow;
vector<int> pref;
 
int gethash(int l, int r){
    int h = ((pref[r+1] - (binpow[r-l+1] * pref[l]))%M + M)%M;
    return h;
}

signed main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t;
    cin >> t;
    while (t--){
        string s;
        cin >> s;
        int n = s.size();
        binpow.clear();
        binpow.resize(n);
        binpow[0] = 1;
        for (int i = 1; i<n; i++){
            binpow[i] = (binpow[i-1]*P) % M;
        }
        pref.clear();
        pref.resize(n+1);
        pref[0] = 0;
        for (int i = 1; i<=n; i++){
            pref[i] = ((pref[i-1]*P)+(s[i-1]-'a'+1)) % M;
        }
        int r = 0;
        int ln = 0;
        int ans = 0;
        vector<bool> vis(n);
        int lst = n-1;
        while (r+ln < n/2){
            int st = r; int stt = r+ln;
            int nd = lst-ln; int ndd = lst;
            int one = gethash(st,stt);
            int two = gethash(nd,ndd);
            //cout << st << " " << stt << "  " << nd << " " << ndd << "\n";
            //cout << one << " " << two << "\n\n";
            if (one == two){
                for (int i = st; i<=stt; i++){
                    vis[i] = true;
                }
                for (int i = nd; i<=ndd; i++){
                    vis[i] = true;
                }
                ans += 2;
                r += ln+1;
                lst -= ln+1;
                ln = 0;
            }
            else{
                ln++;
            }
        }
        int bk = 0;
        for (int i = 0; i<n; i++){
            bk += vis[i];
        }
        if (bk != n) ans++;
        cout << ans << '\n';
    }
    return 0;
}

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