179. Largest Number

Given a list of non negative integers, arrange them such that they form the largest number.

For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330.

Note: The result may be very large, so you need to return a string instead of an integer.

class NumbersComparator implements Comparator<String> {
    @Override
    public int compare(String s1, String s2) {
        return (s2 + s1).compareTo(s1 + s2);
    }
}

public class Solution {    
    public String largestNumber(int[] nums) {
        String[] strs = new String[nums.length];
        for (int i = 0; i < nums.length; i++) {
            strs[i] = Integer.toString(nums[i]);
        }
        Arrays.sort(strs, new NumbersComparator());
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < strs.length; i++) {
            sb.append(strs[i]);
        }
        String result = sb.toString();
        int index = 0;
        while (index < result.length() && result.charAt(index) == '0') {
            index++;
        }
        if (index == result.length()) {
            return "0";
        }
        return result.substring(index);
    }
}

public class Solution {    
    public String largestNumber(int[] nums) {
        if (nums == null || nums.length == 0) {
           return "0";
        }
        int sum = 0;
        List<String> list = new ArrayList<String>();
        for(int i=0; i < nums.length; i++) {
            sum += nums[i];
            list.add(String.valueOf(nums[i]));
        }
        if(sum == 0) return "0";
        Collections.sort(list, (x, y) -> -(x+y).compareTo(y+x));
        StringBuilder sb = new StringBuilder();
        for(int i=0; i < list.size(); i++) {
            sb.append(list.get(i));
        }
        
        return sb.toString();
    }
}