Largest Number from given array of integers

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

Example 1:

Input: [10, 2]

Output: 210

Example 2:

Input: [3,30,34,5,9]

Output: 9534330

Solution:

1:  class Solution {  
2:    public String largestNumber(int[] nums) {  
3:      if(nums == null || nums.length == 0)  
4:        return "";  
5:        
6:      String[] s_num = new String[nums.length];  
7:      for(int i = 0; i< nums.length; i++){  
8:        s_num[i] = String.valueOf(nums[i]);  
9:      }  
10:        
11:      Comparator<String> comp = new Comparator<String>(){  
12:        @Override()  
13:        public int compare(String s1, String s2){  
14:          String str1 = s1+s2;  
15:          String str2 = s2+s1;  
16:          return str2.compareTo(str1);  
17:        }  
18:      };  
19:        
20:      Arrays.sort(s_num, comp);  
21:      if(s_num[0].charAt(0) == '0')  
22:        return "0";  
23:        
24:      StringBuffer sb = new StringBuffer();  
25:      for(String s: s_num){  
26:        sb.append(s);  
27:      }  
28:        
29:      return sb.toString();  
30:    }  
31:  }  

Let's assume:
the length of input array is n,
The average length of Strings in s_num is k,
Comparing two strings will take O(k).
Sorting will take O(nlogn)
Appending to StringBuilder takes O(n).
So total will be O(nklognk) + O(n) = O(nklognk).

Space complexity: O(n).