KMP算法

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

class KMPSearch{
public:
    static void preKMP(string pattern ,int f[] ){
        int m = pattern.length();
        int k;
        f[0] = -1;
        for(int i=1;i<m;i++){
            k = f[i-1];
            while(k>=0){
                if(pattern[k]==pattern[i-1]) break;
                else  k = f[i];
            }
            f[i] = k+1;
        }
    }

    static int KMP(string pattern , string target){
        int m = pattern.length();
        int n = target.length();
        int* f= new int[m];
        preKMP(pattern,f);
        int i=0;
        int k=0;
        while(i<n){
            if(k == -1){
                i++;
                k = 0;
            }else if(target[i] == pattern[k]){
                i++;
                k++;
                if(k == m)
                    return i - (pattern.length());
            }else{
                k = f[k];
            }
        }
        return -1;
    }

    static void test(string pat,string tar){
        cout<<"模式： "<<pat<<endl;
        cout<<"语料： " <<tar<<endl;    
        if(KMP(pat,tar)!=-1){
            cout<<"YES "<<KMP(pat,tar)<<endl;
        }else{
            cout<<"NO"<<endl;
        }
    }    
};
                
int main(){
    string tar = "san and linux traininglin";
    string pat = "lin";
    KMPSearch ks;
    ks.test(pat,tar);
    getchar();
    return 0;
}