Manacher算法 线性时间求最大回文子串长度

原理性的东西在这里得到：http://www.open-open.com/lib/view/open1419150233417.html

/*Manacher算法*/
#include<iostream>
#include<vector>
#include<map>
#include<stdio.h>
#define maxn 100000
#define min(a,b) a>b?b:a
#define max(a,b) a>b?a:b
using namespace std;
char str[maxn];       //元字符串
char tmp[2*maxn+1];   //转换后的字符串
int length;
int len[2*maxn+1];
void Get_New()
{
    int i,j;
    tmp[0]='@';                     //字符串开头增加一个特殊字符，防止越界
    for(i = 1;i <= 2*length;i += 2){
        tmp[i] = '#';
        tmp[i+1] = str[i/2];
    }
    tmp[2*length+1]='#';
}
int Manacher()
{
    int i;
    int mid,maxlen,ans;
    len[0] = 1;
    mid = ans = maxlen = 0;
    for(i = 1;i <= 2*length+1;i ++){
        if(maxlen > i){
            len[i] = min(maxlen-i,len[2*mid-i]);
        }
        else{
            len[i] = 1;
        }
        while(tmp[i-len[i]] == tmp[i+len[i]])
                len[i] ++;
        printf("len[%d] = %d ",i,len[i]);
        printf("
");
        if(len[i] + i > maxlen){
            maxlen = len[i] + i;
            mid = i;
        }
        ans = max(ans,len[i]);
    }
    return ans - 1;
}
int main(void)
{
    int i,ans,pos;
    cin >>length;
    for(i = 0;i < length;i++)
        cin >> str[i];
    Get_New();
    ans = Manacher();
    cout <<ans <<endl;
    return 0;
}