Leetcode OJ : Implement strStr() [ Boyer–Moore string search algorithm ] python solution

class Solution {
public:
int strStr(char *haystack, char *needle) {
    
    int i = 0 , skip[256];
    char *str = haystack, *substr = needle;
    int len_src = strlen(str), len_sub = strlen(substr);
    // preprocess
    for (i = 0; i < 256; i++)
        skip[i] = len_sub;
    int last = len_sub - 1;
    for (i = 0; i < last;i++)
        skip[substr[i]] = last - i;
    // search
    int pos = 0,  j;
    while (pos <= len_src-len_sub)  {
        j = last;
        while (j>=0 && str[pos+j]==substr[j])
            j--;
        if (j<0) 
             return pos;
        pos += skip[str[pos+last]];
    }
    return -1;
}
};