Reorder array to construct the minimum number

Construct minimum number by reordering a given non-negative integer array. Arrange them such that they form the minimum number.

Notice

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

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Example

Given [3, 32, 321], there are 6 possible numbers can be constructed by reordering the array:

3+32+321=332321
3+321+32=332132
32+3+321=323321
32+321+3=323213
321+3+32=321332
321+32+3=321323

So after reordering, the minimum number is 321323, and return it.

分析：

这里需要对数组进行排序，那么怎么比较大小呢？对于数A和B，如果AB在一起组成的数小于BA组成的数，我们就认为A<B,反之亦然。

 public static String minNumber(int[] nums) {
     if (nums == null || nums.length == )
         return "";

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

     Arrays.sort(strs, new Comparator<String>() {
         public int compare(String str1, String str2) {
             return (str1 + str2).compareTo(str2 + str1);
         }
     });

     StringBuilder sb = new StringBuilder();
     for (String str : strs) {
         sb.append(str);
     }
     for (int i = ; i < sb.length(); i++) {
         if (sb.charAt(i) != '') {
             return sb.substring(i);
         }
     }
     return "";
 }