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Author: jimit105

2473-max-sum-of-a-pair-with-equal-sum-of-digits/README.md

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+<p>You are given a <strong>0-indexed</strong> array <code>nums</code> consisting of <strong>positive</strong> integers. You can choose two indices <code>i</code> and <code>j</code>, such that <code>i != j</code>, and the sum of digits of the number <code>nums[i]</code> is equal to that of <code>nums[j]</code>.</p>
+
+<p>Return <em>the <strong>maximum</strong> value of </em><code>nums[i] + nums[j]</code><em> that you can obtain over all possible indices </em><code>i</code><em> and </em><code>j</code><em> that satisfy the conditions.</em></p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [18,43,36,13,7]
+<strong>Output:</strong> 54
+<strong>Explanation:</strong> The pairs (i, j) that satisfy the conditions are:
+- (0, 2), both numbers have a sum of digits equal to 9, and their sum is 18 + 36 = 54.
+- (1, 4), both numbers have a sum of digits equal to 7, and their sum is 43 + 7 = 50.
+So the maximum sum that we can obtain is 54.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [10,12,19,14]
+<strong>Output:</strong> -1
+<strong>Explanation:</strong> There are no two numbers that satisfy the conditions, so we return -1.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>1 &lt;= nums[i] &lt;= 10<sup>9</sup></code></li>
+</ul>

2473-max-sum-of-a-pair-with-equal-sum-of-digits/solution.py

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+# Approach: Hashmap
+
+# m = number of unique sums in `nums`
+# Time: O(n * log n)
+# Space: O(m)
+
+class Solution:
+    def maximumSum(self, nums: List[int]) -> int:
+        digit_sum_dict = {}
+        max_sum = -1
+
+        for num in nums:
+            digit_sum = sum(int(digit) for digit in str(num))
+
+            if digit_sum in digit_sum_dict:
+                max_sum = max(max_sum, digit_sum_dict[digit_sum] + num)
+                digit_sum_dict[digit_sum] = max(digit_sum_dict[digit_sum], num)
+            else:
+                digit_sum_dict[digit_sum] = num
+
+        return max_sum
+