【KMP算法】字符串匹配

#include <iostream>
#include <string>
using namespace std;

//计算next数组
void get_next(string& T, int* next)
{
int i = 0, j = -1, Tlen = T.length();
next[0] = -1;
while(i < Tlen)
{
if(j == -1 || T[i] == T[j])
{
++i;
++j;
next[i]=(T[i] == T[j] ? next[j]:j);//使得回溯前和回溯后的元素不一样
}
else
j = next[j];
}
}

//计算T在S中出现的次数
int subStrCnt(string& S, string& T)
{
int cnt = 0;
int Slen = S.length(), Tlen = T.length();
int next[10000];
int i = 0, j = 0;
get_next(T, next);
while(i < Slen && j < Tlen)
{
if(j == -1 || S[i] == T[j])
{
++i;
++j;
}
else
j = next[j];
if(j == Tlen){//T匹配完成，从T: next[j]再开始
cnt++;
j = next[j];
}
}
return cnt;
}
int main()
{
int cnt;
string S, T;
cin>>cnt;
while(cnt-- > 0)
{
cin>>T>>S;
cout<<subStrCnt(S, T)<<endl;
}
return 0;
}