Submission #506167

#	Time	Username	Problem	Language	Result	Execution time	Memory
506167		Lobo	Palindromic Partitions (CEOI17_palindromic)	C++17	100 / 100	299 ms	28480 KiB

palindromic

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

const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()

#define maxn 1100000

int n;
int mdh = 1e9 + 7;
int pwh[maxn], hsh[maxn];

void prephash(string s) {
    pwh[0] = 1;
    pwh[1] = 5131;
    for(int i = 2; i <= n; i++) {
        pwh[i] = pwh[i-1]*pwh[1];
        pwh[i]%= mdh;   
    }

    hsh[0] = 0;
    for(int i = 1; i <= n; i++) {
        hsh[i] = (hsh[i-1]*pwh[1] + s[i-1])%mdh;
    }
}

int subhash(int l, int r) {
    return ((hsh[r]- hsh[l-1]*pwh[r-l+1])%mdh + mdh)%mdh;
}

void solve() {
    string s; cin >> s;
    n = s.size();
    prephash(s);

    int ans = 0;
    int l = 1, r = n;
    int i = 0;
    while(l+i < r-i) {
        if(subhash(l,l+i) == subhash(r-i,r)) {
            l = l+i+1;
            r = r-i-1;
            i = 0;
            ans+= 2;
        }
        else {
            i++;
        }
    }

    if(l <= r) ans++;

    cout << ans << endl;
}

int32_t main() {
    ios::sync_with_stdio(false); cin.tie(0);

    // freopen("in.in", "r", stdin);
    //freopen("out.out", "w", stdout);

    int tt = 1;
    cin >> tt;
    while(tt--) solve();

}

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