【字符串】【扩展kmp模板】

/*主函数里初始化和调用*/
/*next[0] = 0;
exkmp(s2+1,s2,next+1,next);
exkmp(s1,s2,ex,next);*/
/*扩展kmp算法可以用o(n+m)的复杂度求出字符串s1的任意后缀与字符串s2的最长公共前缀*/
/*扩展kmp算法的next[i]==j表示s2的以s2[i]为起始的后缀与串本身的最长公共前缀长度*/
/*ex[i]为s1[i..]与s2的最长公共前缀，next[i]为s2[i..]与s2的最长公共前缀*/
void exkmp(char s1[],char s2[],int ex[],int next[])
{
	int i,j,p;
	i = j = 0;
	p = -1;
	while(s1[i]!='')
	{
		if( p == -1)
		{
			j = 0;
			do
				p++;
			while(s1[i+p] != ''&&s1[i+p] == s2[j+p]);
			ex[i] = p;
		}
		else if(next[j] < p)
			ex[i] = next[j];
		else if(next[j] > p)
			ex[i] = p;
		else
		{
			j = 0;
			while(s1[i+p] != ''&&s1[i+p] == s2[j+p])
				p++;
			ex[i] = p;
		}	
		
		i++;
		j++;
		p--;
	}
	ex[i] = 0;
	return;
}