Manacher

其实我并没有完全弄懂……所以我写的是自己改编过的。hdu3068过了。

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
char s[110000 << 2],z[110000 << 2];
int p[110000 << 2],len;

void manacher(){
	int id(0),mx(0);
	memset(p,0,sizeof(p));
	p[0] = 1;
	for (int i=1;i<=len;i++){
		p[i] = (mx<i) ? 1:min(p[(id << 1)-i],mx-i);
		while (s[i-p[i]] == s[i+p[i]] && i-p[i]>=0 && i+p[i]<=len) p[i]++;
		if (mx<i+p[i]-1)	{mx = i+p[i]-1; id = i;}
	}
	for (int i=1;i<=len;i++)
		if (s[i+p[i]-1]=='*') p[i]--;
}

int main(){
	while (scanf("%s",z)!=EOF){
		len = strlen(z);
		for (int i=0;i<len-1;i++){
			s[i << 1] = z[i];
			s[i*2+1] = '*';
		}
		s[(len-1) << 1] = z[len-1];
		len = (len << 1)-1;
		manacher();
		int ans(1);
		for (int i=1;i<len;i++)
			ans = max(ans,p[i]);
		printf("%d\n",ans);
	}
	return 0;
}