Submission #446513

#	Time	Username	Problem	Language	Result	Execution time	Memory
446513		JasperL	Palindromic Partitions (CEOI17_palindromic)	C++14	100 / 100	413 ms	27816 KiB

palindromic

#include <iostream>
#include <vector>
#include <cmath>
using namespace std;

#define maxn 1000005
typedef long long ll;
ll mod = 1e9 + 7;
ll p = 29;

string s; int n; vector<int> ret;
ll h[maxn]; // hash values
ll pw[maxn];

bool match(int i, int j, int len) {
    // if [i ... i+len) == [j ... j+len)
    ll H1 = h[i+len-1] - pw[len] * h[i-1]; H1 %= mod; if (H1 < 0) H1 += mod;
    ll H2 = h[j+len-1] - pw[len] * h[j-1]; H2 %= mod; if (H2 < 0) H2 += mod;
    return H1 == H2;
}

void solve() {
    n = s.length(); s = '$' + s;
    for (int i = 1; i <= n; i++) {
        h[i] = h[i-1] * p + (s[i]-'a'); h[i] %= mod;
    }
    int l = 1, r = n;
    int ans = 0;
    for (int i = 1, j = n; i < j; i++, j--) {
        if (match(l,j,i-l+1)) {
            ans += 2; l = i+1; r = j-1; continue;
        }
    }   
    if (l <= r) ans++;
    ret.push_back(ans);
}  

int main() {
    int t; cin >> t; 
    pw[0] = 1;
    for (int i = 1; i < maxn; i++) pw[i] = (pw[i-1] * p)%mod;
    for (int i = 0; i < t; i++) {
        cin >> s; solve();
    }
    for (int z : ret) cout << z << endl;
}

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