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.

 

ref http://blog.csdn.net/whuwangyi/article/details/42705317

"这题最简单的方法其实是，比较两个字符串s1和s2时，比较s1+s2和s2+s1即可。注意这里有一个特殊情况，就是组合后的字符串以0开始，需要把开始的0都去掉。"

对这个comparator的解法很不熟悉

学习一下

 

    public class StringComparator implements Comparator<String>{
        public int compare(String s1, String s2){
            String s12 = s1+s2;
            String s21 = s2+s1;
            return (int) (Long.parseLong(s12) - Long.parseLong(s21));
        }
    }
    public String largestNumber(int[] nums) {
        if(nums==null||nums.length==0) return null;
        List<String> list = new ArrayList<String>();
        StringBuilder sb =  new StringBuilder();
        for(int i:nums) list.add(""+i);
        Collections.sort(list, new StringComparator());
        if(list.get(list.size()-1).equals("0")) return "0";
        for(String i:list){
            sb.insert(0,i);
        }
        return sb.toString();
    }