[LeetCode] 179. Largest Number

Given a list of non-negative integers nums, arrange them such that they form the largest number.

Note: The result may be very large, so you need to return a string instead of an integer.

Example 1:

Input: nums = [10,2]
Output: "210"

Example 2:

Input: nums = [3,30,34,5,9]
Output: "9534330"

Example 3:

Input: nums = [1]
Output: "1"

Example 4:

Input: nums = [10]
Output: "10"

Constraints:

  • 1 <= nums.length <= 100
  • 0 <= nums[i] <= 109

最大数。

题意是给一个整数数组,请将他们拼接成字符串,返回数字最大的字符串。

思路是需要自己写一个comparator函数比较每两个数字拼接结果的字典序,举个例子,需要比较到底是210的字典序大还是102的字典序大。这道题没什么算法,考察的是是否能自己实现一个自定义的comparator函数。JavaScript因为没有数据类型的限制的关系,可以直接比较两个数字的大小。

时间O(n^2) - sort函数最坏情况下

空间O(n)

Java实现

 1 class Solution {
 2     public String largestNumber(int[] nums) {
 3         // corner case
 4         if (nums == null || nums.length == 0) {
 5             return "";
 6         }
 7 
 8         // normal case
 9         int n = nums.length;
10         String[] ss = new String[n];
11         for (int i = 0; i < n; i++) {
12             ss[i] = "" + nums[i];
13         }
14         Arrays.sort(ss, (a, b) -> {
15             String sa = a + b;
16             String sb = b + a;
17             return sb.compareTo(sa);
18         });
19 
20         StringBuilder sb = new StringBuilder();
21         for (String s : ss) {
22             sb.append(s);
23         }
24         int len = sb.length();
25         int k = 0;
26         while (k < len - 1 && sb.charAt(k) == '0') {
27             k++;
28         }
29         return sb.substring(k);
30     }
31 }

 

JavaScript实现

 1 /**
 2  * @param {number[]} nums
 3  * @return {string}
 4  */
 5 var largestNumber = function (nums) {
 6     // corner case
 7     if (nums.every(n => n === 0)) {
 8         return '0';
 9     }
10 
11     // normal case
12     nums.sort((n1, n2) => {
13         const s1 = new String(n1);
14         const s2 = new String(n2);
15         const first = s1 + s2;
16         const second = s2 + s1;
17         if (first > second) {
18             return -1;
19         } else if (first < second) {
20             return 1;
21         } else return 0;
22     });
23     return nums.join('');
24 };

 

LeetCode 题目总结

posted @ 2020-03-24 02:18  CNoodle  阅读(182)  评论(0)    收藏  举报