246. Strobogrammatic Number

首先找到那几种是可以Strobogrammatic的

然后一个walker,一个runner，然后walker <= runner的时候比较是否是一组一组的

要等于因为2就并不是Strobogrammatic

 

    public boolean isStrobogrammatic(String num) {
        Map<Character, Character> map = new HashMap<Character, Character>();
        map.put('6', '9');
        map.put('9', '6');
        map.put('1', '1');
        map.put('8', '8');
        map.put('0', '0');
        int walker = 0;
        int runner = num.length() - 1;
        while(walker <= runner) {
            if(map.containsKey(num.charAt(walker)) && map.get(num.charAt(walker)) == num.charAt(runner)) {
                walker++;
                runner--;
            } else {
                return false;
            }
        }
        return true;
    }