Submission #826515

#	Time	Username	Problem	Language	Result	Execution time	Memory
826515		QwertyPi	Necklace (Subtask 1-3) (BOI19_necklace1)	C++14	17 / 85	1014 ms	392 KiB

necklace

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

struct answer{
	int a, x, y;
};

const int P = 1e9 + 7, A = 13895;
const int N = 3e4 + 11;
int norm(int x){
	return (x % P + P) % P;
}

int h_s[N], h_t[N], pw[N];

int hash_s(int i, int l){
	return norm(h_s[i + l] - h_s[i] * pw[l]);
}

int hash_t(int i, int l){
	return norm(h_t[i + l] - h_t[i] * pw[l]);
}

answer query(const string& s, const string& t){
	int n = s.size(), m = t.size();
	h_s[0] = 0; for(int i = 0; i < n; i++) h_s[i + 1] = (h_s[i] * A + s[i] - 'a') % P;
	h_t[0] = 0; for(int i = 0; i < m; i++) h_t[i + 1] = (h_t[i] * A + t[i] - 'a') % P;
	pw[0] = 1; for(int i = 0; i < max(n, m); i++) pw[i + 1] = pw[i] * A % P;

	answer ans {-1, 0, 0};
	for(int i = 0; i < n; i++){
		for(int j = 0; j < m; j++){
			int lo = 0, hi = min(n - i, m - j);
			while(lo != hi){
				int mid = (lo + hi + 1) / 2;
				if(hash_s(i, mid) == hash_t(j, mid)){
					lo = mid;
				}else{
					hi = mid - 1;
				}
			}
			answer ans_new {lo, i, j};
			if(ans_new.a > ans.a){
				ans = ans_new;
			}
		}
	}
	return ans;
}

int32_t main(){
	string s, t; cin >> s >> t;
	answer a1 = query(s, t);
	reverse(t.begin(), t.end());
	answer a2 = query(s, t); a2.y = t.size() - (a2.y + a2.a);

	answer ans; ans.a = -1;
	if(a1.a > ans.a) ans = a1;
	if(a2.a > ans.a) ans = a2;
	cout << ans.a << endl;
	cout << ans.x << ' ' << ans.y << endl; 
}

• Subtask 1: 5 / 25
• Subtask 2: 4 / 20
• Subtask 3: 8 / 40