leetcode 179 Largest Number

lc179 Largest Number

The main test comparator rewrite, the idea is very simple

The int [] turn into String [], and then descending row

The results can then turn into the string lined up

How to sort? According to what rules?

Look at a few examples

"9" "987" -> "9987" > "9879"

"123" "213" -> "123213" < "213123"

This shows that we need only compare s1 + s2? S2 + s1 to

It should be rewritten to use comparator

. 1 Comparator <String> COM = new new Comparator <String> () {
 2              // @Override 
. 3              public  int Compare (String S1, S2 String) { // Note that the return value int, the return value == 0, s1 == S2;> 0, S1> S2; <0, S2 <S1 
. 4                  String TMP1 = S1 + S2;
 . 5                  String TMP2 = S2 + S1;
 . 6                  return tmp2.compareTo (TMP1); // the compareTo () returns the value is int, supra rules ; but since compare is ranked by ascending order of default, that is> 0 element rows behind, so here we use tmp2.compareTo () 
. 7              }
 . 8          };

There is a corner case, if the original int [] is a bunch of [0, 0, 0, 0], will return to "0000", so we have to consider the case

 1 class Solution {
 2     public String largestNumber(int[] nums) {
 3         if(nums == null || nums.length == 0){
 4             return "";
 5         }
 6         
 7         String[] res = new String[nums.length];
 8         
 9         for(int i=0; i<nums.length; i++){
10             res[i] = String.valueOf(nums[i]);
11         }
12         
13         Comparator<String> com = new Comparator<String>(){
14             //@Override
15             public int compare(String s1, String s2){
16                 String tmp1 = s1+s2;
17                 String tmp2 = s2+s1;
18                 return tmp2.compareTo(tmp1);
19             }
20         };
21         
22         Arrays.sort(res, com);
23         if(res[0].charAt(0) == '0')
24             return "0";
25         
26         StringBuilder sb = new StringBuilder();
27         for(String i :res)
28             sb.append(i);
29         
30         return sb.toString();
31     }
32 }