最长回文
Time Limit: 4000/2000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 26767 Accepted Submission(s): 9783
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
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
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
aaaa abab
Sample Output
4 3
Source
2009 Multi-University Training Contest 16 - Host by NIT
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#include<iostream>
#include<algorithm>
#include<string.h>
using namespace std;
const int N=200020;
char newstr[2*N],str[N];
int p[2*N];
int manacher()
{int i;newstr[0]='$';newstr[1]='#';for(i=1;str[i];i++)newstr[2*i]=str[i], newstr[2*i+1]='#';newstr[2*i]='\0';int res=0,id=0,mx=0;for(int i=2;newstr[i];i++){p[i]=i<mx?min(mx-i,p[2*id-i]):1;while(newstr[i-p[i]]==newstr[i+p[i]])p[i]++;if(p[i]+i>mx)id=i,mx=p[i]+i;res=max(res,p[i]);}return res-1;
}
int main()
{while(~scanf("%s",str+1)){printf("%d\n",manacher());}return 0;
}