Submission #585544

#	Time	Username	Problem	Language	Result	Execution time	Memory
585544		talant117408	Palindromic Partitions (CEOI17_palindromic)	C++17	100 / 100	300 ms	27948 KiB

palindromic

#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
 
#define pb                  push_back
#define mp                  make_pair
#define all(v)              (v).begin(),(v).end()
#define rall(v)             (v).rbegin(),(v).rend()
#define lb                  lower_bound
#define ub                  upper_bound
#define sz(v)               int((v).size())
#define do_not_disturb      ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define endl                '\n'

const int mod = 1e9 + 7;

ll get(int i, int len, vector <ll> &pw, vector <ll> &hash) {
    auto res = hash[i + len - 1];
    if (i) res = ((res - hash[i - 1]) % mod + mod) % mod;
    return res;
}

void solve() {
    string s;
    cin >> s;
    int n = sz(s);
    
    const int P = 37;
    vector <ll> pw(n), hash(n);
    pw[0] = 1;
    for (int i = 1; i < n; i++) {
        pw[i] = ((pw[i - 1] * P) % mod + mod) % mod;
    }
    for (int i = 0; i < n; i++) {
        hash[i] = (((s[i] - 'a' + 1) * pw[i]) % mod + mod) % mod;
        if (i) hash[i] = ((hash[i] + hash[i - 1]) % mod + mod) % mod;
    }
    int l = 0, r = n - 1;
    int ans = 0;
    for (int step = 0; step < n - step - 1; step++) {
        int l1 = step;
        int r1 = n - step - 1;
        auto ans1 = ((get(l, l1 - l + 1, pw, hash) * pw[r1 - l]) % mod + mod) % mod;
        auto ans2 = get(r1, r - r1 + 1, pw, hash);
        //cout << l << ' ' << l1 << ' ' << r1 << ' ' << r << endl;
        //cout << ans1 << ' ' << ans2 << endl;
        //cout << s.substr(l, l1 - l + 1) << ' ' << s.substr(r1, r - r1 + 1) << endl;
        if (ans1 == ans2) {
            ans += 2;
            l = l1 + 1;
            r = r1 - 1;
        }
    }
    if (l <= r) ans++;
    cout << ans << endl;
}

int main() {
    do_not_disturb
    
    int t = 1;
    cin >> t;
    while (t--) {
        solve();
    }
    
    return 0;
}

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