PALINY - Palindrome dài nhất
Tác giả: flashmt
Ngôn ngữ: C++
#include <bits/stdc++.h>
using namespace std;
const char DUMMY = '.';
int manacher(string s) {
int n = s.size() * 2 - 1;
vector <int> f = vector <int>(n, 0);
string a = string(n, DUMMY);
for (int i = 0; i < n; i += 2) a[i] = s[i / 2];
int l = 0, r = -1, center, res = 0;
for (int i = 0, j = 0; i < n; i++) {
j = (i > r ? 0 : min(f[l + r - i], r - i)) + 1;
while (i - j >= 0 && i + j < n && a[i - j] == a[i + j]) j++;
f[i] = --j;
if (i + j > r) {
r = i + j;
l = i - j;
}
int len = (f[i] + i % 2) / 2 * 2 + 1 - i % 2;
if (len > res) {
res = len;
center = i;
}
}
return res;
}
int main() {
int n;
char s[100100];
scanf("%d%s", &n, s);
cout << manacher(string(s, n)) << endl;
}