LintCode: strStr

C++

(1) null

(2) length is 0

(3) return value

(4) strlen

class Solution {
public:
    /**
     * Returns a index to the first occurrence of target in source,
     * or -1  if target is not part of source.
     * @param source string to be scanned.
     * @param target string containing the sequence of characters to match.
     */
    int strStr(const char *source, const char *target) {
        // write your code here
        if (source == NULL || target == NULL) return -1;
        
        int i, j, len_s = strlen(source), len_t = strlen(target);
        
        if (len_s == 0 && len_t == 0) return 0;
        
        i = 0;
        while (source[i] != '') {
            if (i + len_t > len_s) return -1;
            j = 0;
            while (target[j] != '') {
                if (source[i + j] == target[j]) {
                    j++;
                } else {
                    break;
                }
            }
            if (target[j] == '')  return i;
            i++;
        }
        return -1;
    }
};