KMP算法 C++实现

#include <iostream>
#include <string>
#include <vector>
using namespace std;
void getNext(const string &substr, vector<int> &next)
{
next.clear();
next.resize(substr.size());
int j = -1;
next[0] = -1;
for(int i = 1; i < substr.size(); ++i)
{
while(j > -1 && substr[j + 1] != substr[i])
j = next[j];
if(substr[j + 1] == substr[i])
++j;
next[i] = j;
}
}
void kmp(const string &str, const string &substr, vector<int> &next)
{
int cnt = 0;
getNext(substr, next);
int j = -1;
for(int i = 0; i < str.size(); ++i)
{
while(j > -1 && substr[j + 1] != str[i])
j = next[j];
if(substr[j + 1] == str[i])
++j;
if(j == substr.size() - 1)
{
cout << "find in position" << i << endl;
++cnt;
j = next[j];
}
}
if(cnt == 0)
cout << "not find" << endl;
}
int main()
{
string str, substr;
cin >> str >> substr;
vector<int> next;
kmp(str, substr, next);
return 0;
}