目录

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.

思路

这道题目思路很清晰，就是先将int num数组转换为String num数组，然后对其进行排序。排序的规则如下：

例如字符串str1和str2，拼接字符串cmp1 = str1 + str2，cmp2 = str2 + str1。按照字典排序，如果cmp1 > cmp2，则str1 > str2。反之，则str1 < str2。
注意：这里可以使用Java提供的Comparator接口，然后实现字典逆序。

Cpmparator接口使用可以参考我的这篇博客：Comparator和Comparable的区别使用。

AC代码

AC的代码如下：

public class Solution {
    public static String largestNumber(int[] num) {
        StringBuilder res = new StringBuilder();

        String[] numArrays = new String[num.length];
        int zeroNum = 0;
        for (int i = 0; i < num.length; i ++) {
            if (num[i] == 0) {
                zeroNum ++;
            }
            numArrays[i] = Integer.toString(num[i]);
        }

        if (zeroNum == num.length) {
            return "0";
        }

        Arrays.sort(numArrays, new NumComparator());

        for (String s : numArrays) {
            res.append(s);
        }      
        return res.toString();
    }


    private static class NumComparator implements Comparator<String> {

        @Override
        public int compare(String str1, String str2) {
            String cmp1 = str1 + str2;
            String cmp2 = str2 + str1;

            return cmp1.compareTo(cmp2) * -1;
        }

    }
}