HDOJ 2087

// HDOJ 2087 KMP算法
#include<iostream>
using namespace std;

#include<string>

void nextval(char s2[],int next[],int len)
{
next[1] = 0;
int i = 1,j = 0;
while(i < len)//这里是小于号而不是小于等于是因为里面有自加，防止越界！
{
if(j == 0 || s2[i] == s2[j])
{
++i;
++j;
if(s2[i] != s2[j]) next[i] = j;
else next[i] = next[j];
}
else j = next[j];
}
}

int KMP(char s1[],char s2[],int len1,int len2,int next[],int pos)
{
int i = pos,j = 1;
while(i <= len1 && j <= len2)
{
if(j == 0 || s1[i] == s2[j])
{
++i;
++j;
}
else j = next[j];
}
if(j > len2) return i;
else return 0;
}

int main()
{
string s1,s2;
while(cin>>s1 && s1 != "#")
{
cin>>s2;
int next[s2.size()+1],c = 0,pp = 0;
next[0] = -1;
char c1[s1.size()+1],c2[s2.size()+1];
for(int i = 1;i <= s1.size();++i) c1[i] = s1[i-1];
for(int i = 1;i <= s2.size();++i) c2[i] = s2[i-1];
nextval(c2,next,s2.size());
for(int pos = 1;pos <= s1.size();)
{
pp = KMP(c1,c2,s1.size(),s2.size(),next,pos);
if(pp)
{
++c;
pos = pp;
}
else break;
}
cout<<c<<endl;
}

return 0;
}