【模板】KMP
int next[N];
char str1[M],str2[N];
//str1 长，str2 短
//len1,len2,对应str1,str2的长 void get_next(int len2)
{
int i = ,j = -;
next[] = -;
while(i<len2)
{
if(j == - || str2[i] == str2[j])
{
i++;
j++;
if(str2[i] != str2[j])
next[i] = j;
else
next[i] = next[j];
}
else
j = next[j];
}
//计算某字符串的周期，如aaaa是4，abcd是1
/*
int i = 0;j = -1;
next[0] = -1;
while(str2[i])
{
if(j == -1 || str2[i] == str2[j])
{
i++;j++;
next[i] = j;
}
else
j = next[j];
}
len = strlen(str);
i = len-j;
if(len%i==0)
return len/i;
else
return 1;
*/
} int kmp(int len1,int len2)
{
int i = ,j = ;
get_next(len2);
while(i<len1)
{
if(j == - || str1[i] == str2[j])
{
i++;
j++
}
else
j = next[j];
/*
if(j == len2)//计算str2在str1中出现多少次
{
cnt++;
j= next[j];
}
*/
}
//return j; //j为匹配的长度
if(j>len2)
return ;//这里也可以返回i-len2来获得匹配在主串中开始的位置
else
return ;
} //数字KMP
int a[],b[];
int next[],n,m; void getnext()
{
int i = ,j = -;
next[] = -;
while(i<m)
{
if(j == - || b[i] == b[j])
{
i++;
j++;
if(b[i] == b[j])
next[i] = next[j];
else
next[i] = j;
}
else
j = next[j];
}
} int kmp()//返回匹配位置
{
int i = ,j = ;
while(i<n)
{
if(a[i] == b[j])
{
if(j == m-)
return i-j+;
i++;
j++;
}
else
{
j = next[j];
if(j == -)
{
i++;
j = ;
}
}
}
return -;
}