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.

注意：

1. 这里的比较方法是如果 a + b > b + a 则 a > b ， 即 比较 30 和 34 , 因为 3034 < 3430， 所以34 比 30 大。

2. priorityqueue 默认是从小到大输出的。 所以在comparator里面 大的return -1！

 1 public class Solution {

 2 

 3     public String largestNumber(int[] num) {

 4         PriorityQueue<Integer> pq = new PriorityQueue<Integer>(

 5             new Comparator<Integer>() {

 6                 public int compare(Integer a, Integer b){

 7                     StringBuilder sb = new StringBuilder();

 8                     sb.append(a);

 9                     sb.append(b);

10                     int first = Integer.valueOf(sb.toString());

11                     sb = new StringBuilder();

12                     sb.append(b);

13                     sb.append(a);

14                     int second = Integer.valueOf(sb.toString());

15                     if(first > second) return -1;

16                     else if(first == second) return 0;

17                     else return 1;

18                 }

19             }

20         );

21         StringBuilder sb = new StringBuilder();

22         for(int i = 0; i < num.length; i ++){

23             pq.add(num[i]);

24         }

25         for(int i = 0; i < num.length; i ++){

26             sb.append(pq.poll());

27         }

28         return sb.charAt(0) == '0' ? new String("0") : sb.toString();

29     }

30 }