제출 #239634

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
239634		eohomegrownapps	Palindromic Partitions (CEOI17_palindromic)	C++14	100 / 100	495 ms	26744 KiB

palindromic

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll m = 1000000007;
ll p = 31;
ll pows[1000005];
void run(){
	string s;
	cin>>s;
	ll n= s.size();
	vector<ll> arr(n);
	for (ll i = 0; i<n; i++){
		arr[i]=s[i]-'a'+1;
	}
	vector<ll> ltor(n);//1,x+1,x^2+x+1...
	//vector<ll> rtol(n);//...x^2+x+1,x+1,1
	ltor[0]=arr[0];
	for (ll i = 1; i<n; i++){
		ltor[i]=(ltor[i-1]*p+arr[i])%m;
	}
	/*rtol[n-1]=arr[n-1];
	for (ll i = n-2; i>=0; i--){
		rtol[i]=(rtol[i+1]*p+arr[i])%m;
	}*/
	ll cnt = 0;
	ll prevstart = 0;
	for (ll i = 0; i<n; i++){
		//check if prevstart to i forms a block
		ll pref = ltor[i];
		ll sub = prevstart==0?0:(ltor[prevstart-1]*pows[i-prevstart+1])%m;
		ll fwd = (pref-sub+m)%m;

		ll bkstart = n-1-i;
		ll bkend = n-1-prevstart;
		pref = ltor[bkend];
		sub = bkstart==0?0:(ltor[bkstart-1]*pows[bkend-bkstart+1])%m;
		ll bwd = (pref-sub+m)%m;
		if (fwd==bwd){
			cnt+=1;
			prevstart=i+1;
		}
	}
	cout<<cnt<<'\n';
}

int main(){
	cin.tie(0);
	ios_base::sync_with_stdio(0);
	pows[0]=1;
	for (ll i = 1; i<1000005; i++){
		pows[i]=(pows[i-1]*p)%m;
	}
	ll n;
	cin>>n;
	for (ll i = 0; i<n; i++){
		run();
	}
}

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