class Solution {

    /**

     * 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.

     */

    public int strStr(String source, String target) {

        //write your code here

        if(source == null || target == null) return -1;

        if(target.length() == 0) return 0;

        if(source.length() == 0) return -1;

        for(int i = 0; i < source.length(); i++){

            boolean flag = true;

            for( int j = 0; j < target.length(); j++){

                if(source.charAt(i + j) == target.charAt(j)){

                }

                else{

                    flag = false;

                    break;

                }

            }

            if(flag) return i;

        }

        return -1;

    }

}