max-pair-sum-in-an-array

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Algorithms

You are given an integer array <code>nums</code>. You have to find the maximum sum of a pair of numbers from <code>nums</code> such that the largest digit in both numbers is equal.

For example, 2373 is made up of three distinct digits: 2, 3, and 7, where 7 is the largest among them.

Return the maximum sum or -1 if no such pair exists.

&nbsp;
Example 1:

<div class="example-block">
Input: nums = [112,131,411]

Output: -1

Explanation:

Each numbers largest digit in order is [2,3,4].
</div>

Example 2:

<div class="example-block">
Input: nums = [2536,1613,3366,162]

Output: 5902

Explanation:

All the numbers have 6 as their largest digit, so the answer is 2536 + 3366 = 5902.
</div>

Example 3:

<div class="example-block">
Input: nums = [51,71,17,24,42]

Output: 88

Explanation:

Each number&#39;s largest digit in order is [5,7,7,4,4].

So we have only two possible pairs, 71 + 17 = 88 and 24 + 42 = 66.
</div>

&nbsp;
Constraints:

<ul>
	<li><code>2 &lt;= nums.length &lt;= 100</code></li>
	<li><code>1 &lt;= nums[i] &lt;= 104</code></li>
</ul>

maxSum

Max Pair Sum in an Array

Array

Hash Table

给你一个下标从 0 开始的整数数组 <code>nums</code> 。请你从 <code>nums</code> 中找出和 最大 的一对数，且这两个数数位上最大的数字相等。

返回最大和，如果不存在满足题意的数字对，返回 <code>-1</code> 。

&nbsp;

示例 1：

<pre>输入：nums = [51,71,17,24,42]
输出：88
解释：
i = 1 和 j = 2 ，nums[i] 和 nums[j] 数位上最大的数字相等，且这一对的总和 71 + 17 = 88 。 
i = 3 和 j = 4 ，nums[i] 和 nums[j] 数位上最大的数字相等，且这一对的总和 24 + 42 = 66 。
可以证明不存在其他数对满足数位上最大的数字相等，所以答案是 88 。</pre>

示例 2：

<pre>输入：nums = [1,2,3,4]
输出：-1
解释：不存在数对满足数位上最大的数字相等。
</pre>

&nbsp;

提示：

<ul>
	<li><code>2 &lt;= nums.length &lt;= 100</code></li>
	<li><code>1 &lt;= nums[i] &lt;= 104</code></li>
</ul>