Submission #829105

#	Time	Username	Problem	Language	Result	Execution time	Memory
829105		NhanBeoo	Palindromes (APIO14_palindrome)	C++17	23 / 100	1072 ms	22052 KiB

palindrome

// Judges with GCC >= 12 only needs Ofast
// #pragma GCC optimize("Ofast")
#pragma GCC optimize("O3,no-stack-protector,fast-math,unroll-loops,tree-vectorize")
// MLE optimization
// #pragma GCC optimize("conserve-stack")
// Old judges
// #pragma GCC target("sse4.2,popcnt,lzcnt,abm,mmx,fma,bmi,bmi2")
// New judges. Test with assert(__builtin_cpu_supports("avx2"));
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma,tune=native")
// Atcoder
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma")

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

#define int ll
#define MAX LLONG_MAX
#define st first
#define nd second
#define endl '\n'
#define SZ(x) ((int)x.size())
#define ALL(x) x.begin(), x.end()
typedef long long ll;
typedef pair< int, int > ii;
typedef pair< int, ii > iii;
typedef vector< int > vi;
typedef vector< ii > vii;
typedef vector< iii > viii;
typedef vector< vi > vvi;
typedef vector< vii > vvii;
typedef vector< viii > vviii;

const int N = 3e5 + 5;
int n;
int base = 311;
int mod[] = {1000000007, 100313, 500249};
string s, t;
int hashS[3][N], hashT[3][N], power[3][N];
unordered_map<int, int> m;
int ans = 0;

int palind(int l, int r){
	int ans;
	for(int k=0; k<3; k++){
		int tmp1 = (hashS[k][r] - hashS[k][l-1] * power[k][r-l+1] + mod[k] * mod[k]) % mod[k];
		int tmp2 = (hashT[k][n-l+1] - hashT[k][n-r] * power[k][r-l+1] + mod[k] * mod[k]) % mod[k];
		if(tmp1 != tmp2) return -1;
		if(k == 2) ans = tmp1;
	}
	return ans;
}

signed main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	
	cin >> s;
	t = s; reverse(ALL(t));
	n = SZ(s);
	s = ' ' + s;
	t = ' ' + t;
	for(int i=0; i<3; i++){
		power[i][0] = 1;
		for(int j=1; j<=n; j++) power[i][j] = (power[i][j-1] * base) % mod[i];
		hashS[i][0] = s[0];
		for(int j=1; j<=n; j++) hashS[i][j] = (hashS[i][j-1] * base + s[j]) % mod[i];
		hashT[i][0] = t[0];
		for(int j=1; j<=n; j++) hashT[i][j] = (hashT[i][j-1] * base + t[j]) % mod[i];
	}
	for(int len=1; len<=n; len++){
		for(int i=1; i+len-1<=n; i++){
			int hashed = palind(i, i+len-1);
			if(hashed != -1) m[hashed]++;
		}
		for(auto tmp: m){
			int cnt = tmp.nd;
			ans = max(ans, len * cnt);
		}
		m.clear();
	}
	cout << ans;
} 

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 26
• Subtask 5: 0 / 27