UnlockPatternCombination

    public static List<String> findCombo(){
        char[][] keyboard = {{'1', '2', '3'}, {'4', '5', '6'}, {'7', '8', '9'}};
        List<String> result = new ArrayList<String>();
        String tmp = new String();
        for(int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                helper(keyboard, result, tmp, i, j);
            }
        }
        return result;
    }

    public static void helper(char[][] keyboard, List<String> result, String tmp, int i, int j){
        if(tmp.length()==4 && !result.contains(tmp)){
            result.add(new String(tmp));
            return;
        }
        if(i>=3||j>=3||i<0||j<0) return;

        char ch = keyboard[i][j];
        if(tmp.indexOf(ch)<0){
        //if(tmp.length()==0||(tmp.length()>0&&tmp.charAt(tmp.length()-1)!=ch)){
            helper(keyboard, result, tmp+ch, i+1, j);
            helper(keyboard, result, tmp+ch, i, j+1);
            helper(keyboard, result, tmp+ch, i+1, j+1);
            helper(keyboard, result, tmp+ch, i-1, j);
            helper(keyboard, result, tmp+ch, i, j-1);
            helper(keyboard, result, tmp+ch, i-1, j-1);
            helper(keyboard, result, tmp+ch, i+1, j-1);
            helper(keyboard, result, tmp+ch, i-1, j+1);
        }
    }

    public static void main(String args[]){
        List<String> result = findCombo();
        for(String str : result){
            System.out.println(str);
        }
        System.out.println("Total combinations: "+result.size());
    }