poj3974 Palindrome(Manacher最长回文)

之前用字符串hash+二分过了，今天刚看了manacher拿来试一试。

这manacher也快太多了%%%

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

const int maxn = 1e6 + 5;
char s[maxn], tmp[2*maxn];
int p[maxn*2], id, mx, ans;
inline void manacher(){
    mx = id = ans = 0;
    memset( p, 0, sizeof(p) );
    for( int i=1; tmp[i]; i++ ){
        p[i] = mx>i ? min(p[2*id-i], mx-i):1;　　　　//因为i >= id 所以找其在左侧已经求出的对称点2*id-1
        while( tmp[i+p[i]]==tmp[i-p[i]] ) p[i]++;
        if( mx<i+p[i] ){
            mx = i+p[i];
            id = i;
        }
    }
    for( int i=1; tmp[i]; i++ )
        if( ans<p[i] ) ans = p[i];
}

int main(){
    int kase = 0;
    while( ~scanf("%s", s+1) && s[1]!='E' ){
        int len = strlen(s+1);
        tmp[0] = '$';
        int j = 2;
        for( int i=1; i<=len; i++, j+=2 ){
            tmp[j+1] = tmp[j-1] = '#';
            tmp[j] = s[i];
        }
        tmp[j+2] = 0;
        manacher();
        printf("Case %d: %d
", ++kase, ans-1);
    }

    return 0;
}
/*
Sample Input

abcbabcbabcba
abacacbaaaab
END
Sample Output

Case 1: 13
Case 2: 6
*/