杭电3068 最长回文 最长回文的manacher算法

最长回文

Time Limit: 4000/2000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 12275    Accepted Submission(s): 4514

Problem Description

给出一个只由小写英文字符a,b,c...y,z组成的字符串S,求S中最长回文串的长度.
回文就是正反读都是一样的字符串,如aba, abba等

 

Input

输入有多组case,不超过120组,每组输入为一行小写英文字符a,b,c...y,z组成的字符串S
两组case之间由空行隔开(该空行不用处理)
字符串长度len <= 110000

 

Output

每一行一个整数x,对应一组case,表示该组case的字符串中所包含的最长回文长度.

 

Sample Input

aaaaabab

 

Sample Output

43

 

Source

2009 Multi-University Training Contest 16 - Host by NIT

 

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我就不详解了看这里 http://blog.csdn.net/xingyeyongheng/article/details/9310555

附ac代码：

#include<stdio.h>#include<string.h>#include<algorithm>using namespace std;char s[330000];int i,j,k,l,p[330000],m,n,id,Maxlen;int main(){while(scanf("%s",s)!=EOF){l=strlen(s);for(i=l;i>=0;i--){s[2*i+1]='#';s[2*i+2]=s[i];}id=0;Maxlen=0;s[0]='*';for(i=2;i<2*l+1;i++){if(p[id]+id>i)p[i]=min(p[2*id-i],p[id]+id-i);elsep[i]=1;while(s[i-p[i]]==s[i+p[i]])p[i]++;if(id+p[id]<i+p[i])id=i;if(Maxlen<p[i])Maxlen=p[i];}printf("%d\n",Maxlen-1);}}