Leetcode no. 179

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.

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

class LargestNumberComparator implements Comparator<String>{
    @Override
    public int compare(String o1, String o2) {
        return (o2+o1).compareTo(o1+o2);
    }
}