POJ (Manacher) Palindrome

多敲几个模板题，加深一下对Manacher算法的理解。

这道题给的时间限制15s，是我见过的最长的时间的了。看来是为了让一些比较朴素的求最大回文子串的算法也能A过去

Manacher算法毕竟给力，运行时间200+MS

//#define LOCAL
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

const int maxn = 1000000 + 100;
char s1[maxn], s2[maxn * 2];
int p[maxn * 2];

void Init(void)
{
    s2[0] = '$', s2[1] = '#';
    int j = 2;
    for(int i = 0; s1[i] != ''; ++i)
    {
        s2[j++] = s1[i];
        s2[j++] = '#';
    }
    s2[j] = '';
}

void manacher(char s[])
{
    int id, mx = 0;
    p[0] = 0;
    for(int i = 1; s[i] != ''; ++i)
    {
        if(mx > i)
            p[i] = min(p[id*2-i], mx-i);
        else
            p[i] = 1;
        while(s[i + p[i]] == s[i - p[i]])
            ++p[i];
        if(i + p[i] > mx)
        {
            mx = i + p[i];
            id = i;
        }
    }
}

int getans(void)
{
    int ans = 1;
    for(int i = 1; s2[i] != ''; ++i)
        ans = max(ans, p[i] - 1);
    return ans;
}

int main(void)
{
    #ifdef LOCAL
        freopen("3974in.txt", "r", stdin);
    #endif

    int kase = 1;
    while(scanf("%s", s1) != EOF)
    {
        if(s1[0] == 'E')    break;
        Init();
        manacher(s2);
        printf("Case %d: %d
", kase++, getans());
    }
    return 0;
}