hihocoder1032 最长回文子串

思路：

manacher模板。

实现：

#include <iostream>
#include <cstring>
using namespace std;
int p[2000005];
string init(string s)
{
    string res = "$#";
    for (int i = 0; i < s.length(); i++)
    {
        res += s[i]; res += '#';
    }
    return res;
}
int main()
{
    int n;
    cin >> n;
    string s;
    while (n--)
    {
        cin >> s;
        memset(p, 0, sizeof p);
        s = init(s);
        int r = 0, id = 0, maxn = 0;
        for (int i = 1; i < s.length(); i++)
        {
            if (i < r) p[i] = min(r - i, p[2 * id - i]);
            else p[i] = 1;
            int j = p[i];
            while (s[i + j] == s[i - j]) { j++; p[i]++; }
            if (i + p[i] - 1 > r) { r = i + p[i] - 1; id = i; }
            maxn = max(maxn, p[i] - 1);
        }
        cout << maxn << endl;
    }
    return 0;
}