KMP模板

void get_next(char b[], int *next)
{
    int i = 0;
    int j = -1;
    next[i] = -1;
    int len_b = strlen(b);
    while(i < len_b - 1)
    {
        if(j == -1 || b[i] == b[j])
        {
            ++i;
            ++j;
            next[i] = j;
        }
        else
        {
            j = next[j];
        }
    }
}

int kmp_search(char a[], char b[], int next[])
{
    int i = 0;
    int j = 0;
    int len_a = strlen(a);
    int len_b = strlen(b);
    while(i < len_a && j < len_b)
    {
        if(j == -1 || a[i] == b[j])
        {
            ++i;
            ++j;
        }
        else
        {
            j = next[j];
        }
    }
    if(j >= len_b)
    {
        return i - len_b;
    }
    else
    {
        return -1;
    }
}