manacher算法

一篇博客

#include<bits/stdc++.h>
#define re return
#define inc(i,l,r) for(int i=l;i<=r;++i)
#define Min(a,b) (a)<(b)?(a):(b)
#define Max(a,b) (a)>(b)?(a):(b)
using namespace std;
char str[11000005],s[22000005];
int p[22000005];
int main()
{
	int k=-1;
	s[++k]='$';
	scanf("%s",str);
	int len=strlen(str)-1;
	inc(i,0,len)
	s[++k]='#',s[++k]=str[i];
	s[++k]='#';
	s[++k]='[';
	
	
	int mx=0,id=0,sum=0;
	inc(i,1,k)
	{
		if(mx>i)p[i]=Min(mx-i,p[(id<<1)-i]);
		else p[i]=1;
		
		while(s[i+p[i]]==s[i-p[i]])++p[i];
		if(p[i]-1>sum)
		{
			sum=p[i]-1;
			mx=i+p[i];
			id=i;
		}
	}
	
	printf("%d",sum);
	re 0;
}