179. Largest Number

https://leetcode-cn.com/problems/largest-number/

（图片来源https://leetcode-cn.com/problems/largest-number/
）

public String largestNumber(int[] num) {
        if(num == null || num.length == 0) {
            return "";
        }

        // Convert int array to String array, so we can sort later on
        List<String> sNum = Arrays.stream(num).
                mapToObj(String::valueOf).
                sorted((x,y) -> (y+x).compareTo(x+y)).
                collect(Collectors.toList());


        if(sNum.get(0).charAt(0) == '0') {
            return "0";
        }

        return String.join("", sNum);
    }

public String largestNumber2(int[] num) {
        if(num == null || num.length == 0)
            return "";

        // Convert int array to String array, so we can sort later on
        String[] sNum = new String[num.length];
        for(int i = 0; i < num.length; i++){
            sNum[i] = String.valueOf(num[i]);
        }


        Arrays.sort(sNum, (x,y) -> (y+x).compareTo(x+y));
        // An extreme edge case by lc, say you have only a bunch of 0 in your int array
        if(sNum[0].charAt(0) == '0'){
            return "0";
        }
        

        return String.join("", sNum); //  String.join("", s_num) 太耗时间了

    }