179. Largest Number

题目：

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.

链接：http://leetcode.com/problems/largest-number/ 

6/20/2017

最初的想法是改动MSD来排序，但是如果位数不一样需要补前一个高位的char，而不是''，很麻烦。

参考别人的sort方法，很好很强大。

注意：

1. Arrays.sort(), Comparator接口当中要实现compare函数

2. 当输入全是0时返回0

public class Solution {
    public String largestNumber(int[] nums) {
        if (nums == null || nums.length == 0) {
            return "";
        }
        String[] numsInString = new String[nums.length];
        
        for (int i = 0; i < nums.length; i++) {
            numsInString[i] = Integer.toString(nums[i]);
        }
        Arrays.sort(numsInString, new Comparator<String>() {
            public int compare(String s1, String s2) {
                String s1s2 = s1 + s2;
                String s2s1 = s2 + s1;
                return s1s2.compareTo(s2s1);
            }
        });
        if (numsInString[numsInString.length - 1].equals("0")) {
            return "0";
        }
        StringBuilder sb = new StringBuilder();
        for (int i = numsInString.length - 1; i >= 0; i--) {
            sb.append(numsInString[i]);
        }
        return sb.toString();
    }
}

也可以比较的时候直接返回reverse order

https://discuss.leetcode.com/topic/8018/my-java-solution-to-share

Java 8的简介写法

https://discuss.leetcode.com/topic/7235/my-3-lines-code-in-java-and-python

更多讨论

https://discuss.leetcode.com/category/187/largest-number