Largest Number

Give an array of integer, it is asked to return the largest number that if we turn these numbers into string, reorder them and concat them into a new string. It is a sort problem, there are two points we need to take care of:

1. The order of string is not in alphabet order. Say 121 and 12, obviously 12121 is greater than 12112, but if we are using default string compare function, we have "12" < "121".
2. If the greatest number in the array is 0, then we should just return "0" instead of something like "0000".

The code:

public class LargestNumber {
    public String largestNumber(int[] nums) {
        if (nums.length == 0) return "0";

        String[] strs = new String[nums.length];

        for (int i = 0; i < strs.length; i++) {
            strs[i] = String.valueOf(nums[i]);
        }

        Arrays.sort(strs, new Comparator<String>() {
            public int compare(String a, String b) {
                return (a + b).compareTo(b + a);
            }
        });

        for (int i = 0; i < strs.length / 2; i++) {
            String temp = strs[i];
            strs[i] = strs[strs.length - i - 1];
            strs[strs.length - i - 1] = temp;
        }

        if (strs[0].equals("0")) return "0";
        StringBuilder sbd = new StringBuilder();
        for (String s: strs) {
            sbd.append(s);
        }
        return sbd.toString();
    }
}