Manacher算法 线性时间求最大回文子串长度

/*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("\n");
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;
}