KMP算法及其优化

    #include<iostream>  
    #include<cstring>  
    using namespace std;  
      
    void get_next(char* p, int* next)  
    {  
        int i, j;  
        i = 0;  
        j = -1;  
        next[0] = -1;  
        while (i < strlen(p))  
        {  
            if (j == -1 || p[i] == p[j])  
            {  
                i++;  
                j++;  
                //next[i] = j;  
                  
                if (p[i] != p[j])  
                next[i] = j;  
                else  
                next[i] = next[j];  
                  
                //cout << "next[i] = " << j << endl;  
            }  
            else  
            {  
                j = next[j];  
                //cout << "i = " << i << " j = " << j << endl;  
            }  
        }  
    }  
      
    int index_kmp(char* p, char* x)  
    {  
        int i = -1;  
        int j = -1;  
        int len1 = strlen(p);  
        int len2 = strlen(x);  
        int next[100];  
        get_next(x, next);  
        while(i < len1 && j < len2)  
        {  
            if (j == -1 || p[i] == x[j])  
            {  
                i++;  
                j++;  
            }  
            else  
            {  
                j = next[j];  
                //cout << "i = " << i << " j = " << j << endl;  
            }  
        }  
        if (j == strlen(x))  
            return i - strlen(x);  
        else  
            return -1;  
    }  
      
    int main()  
    {  
        char ch[100];  
        char s[100];  
        int next[100];  
        while(1)  
        {  
            cin >> ch;  
            cin >> s;  
            get_next(ch, next);  
            //for (int i = 0; i < strlen(ch); i++)  
                //cout << next[i] << ' ';  
            //cout << endl;  
            int n = index_kmp(s, ch);  
            cout << n << endl;  
        }  
        return 0;  
    }