lessons/参考实现/04-KMP与Manacher/POJ-3974.cpp

#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    string s;
    int test = 0;
    while (cin >> s && s != "END") {
        int n = static_cast<int>(s.size());
        vector<int> d1(n), d2(n);
        for (int i = 0, l = 0, r = -1; i < n; ++i) {
            int k = (i > r) ? 1 : min(d1[l + r - i], r - i + 1);
            while (i - k >= 0 && i + k < n && s[i - k] == s[i + k]) ++k;
            d1[i] = k;
            if (i + k - 1 > r) l = i - k + 1, r = i + k - 1;
        }
        for (int i = 0, l = 0, r = -1; i < n; ++i) {
            int k = (i > r) ? 0 : min(d2[l + r - i + 1], r - i + 1);
            while (i - k - 1 >= 0 && i + k < n && s[i - k - 1] == s[i + k]) ++k;
            d2[i] = k;
            if (i + k - 1 > r) l = i - k, r = i + k - 1;
        }
        int answer = 1;
        for (int x : d1) answer = max(answer, 2 * x - 1);
        for (int x : d2) answer = max(answer, 2 * x);
        cout << "Case " << ++test << ": " << answer << '\n';
    }
}