HDU3068 最长回文

//It is made by ljh2000
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;
typedef long long LL;
const int MAXN = 250011;
int n,p[MAXN],len,ans,maxR,id;
char ch[MAXN],s[MAXN];

inline int getint(){
    int w=0,q=0; char c=getchar(); while((c<‘0‘||c>‘9‘) && c!=‘-‘) c=getchar();
    if(c==‘-‘) q=1,c=getchar(); while (c>=‘0‘&&c<=‘9‘) w=w*10+c-‘0‘,c=getchar(); return q?-w:w;
}

inline void work(){
	while(scanf("%s",ch)!=EOF) {
		len=strlen(ch); n=1;
		s[0]=‘%‘; s[1]=‘#‘;
		for(int i=0;i<len;i++) {
			s[++n]=ch[i];
			s[++n]=‘#‘;
		}
		memset(p,0,sizeof(p)); ans=0;
		maxR=0; id=0;
		for(int i=1;i<=n;i++) {
			if(i<maxR) p[i]=min(p[2*id-i],maxR-i);	else p[i]=1;
			for(;i+p[i]<=n && s[i-p[i]]==s[i+p[i]];p[i]++) ;
			if(i+p[i]>maxR) { maxR=i+p[i]; id=i; }
		}
		for(int i=1;i<=n;i++) ans=max(ans,p[i]); ans--;
		printf("%d\n",ans);
	}
}

int main()
{
    work();
    return 0;
}