Max Sum Of A Pair With Equal Sum Of Digits - Leetcode Solution

Problem Statement:

Given an array of integers nums, find the maximum possible sum of a pair of elements such that the sum is even and both elements have the same number of digits.

If there are multiple pairs that meet the criteria, return the one with the largest sum.

Solution:

The problem requires us to find a pair of elements from the given array that satisfy the given conditions. We need to find the maximum possible sum of such a pair.

The conditions that the sum is even and both elements have the same number of digits are important. We can use these conditions to simplify the problem.

We can iterate through the given array and check each element if it satisfies the conditions. If an element satisfies both conditions, then we can compare its sum with the current maximum sum of the pairs we have seen so far.

We can use two variables to keep track of the maximum sum and the current best pair of elements. We can initialize the maximum sum variable to negative infinity and the best pair variable to None.

For each element, we can check if it is even or odd. If it is odd, we can skip it because the sum of an odd number and another number can never be even. If it is even, we can check the number of digits in the element.

To count the number of digits in an element, we can convert it to a string and use the len() function. If the number of digits is odd, we can skip the element because we cannot form a pair with an odd number of digits. If the number of digits is even, we can check if we have seen another element with the same number of digits before.

We can use a dictionary to store the elements we have seen so far. The keys of the dictionary can be the number of digits, and the values can be a list of elements with that many digits.

For each element with an even number of digits, we can check if we have seen another element with the same number of digits before. If we have, we can compute the sum of the two elements and update the maximum sum and the best pair variables if the sum is greater than the current maximum sum.

At the end, we can return the best pair variable.

Here is the Python code for the solution:

def maxSum(nums): maxSum = float('-inf') bestPair = None seen = {}

for num in nums:
    if num % 2 == 0:
        digits = len(str(num))
        if digits % 2 == 0:
            if digits in seen:
                for pairNum in seen[digits]:
                    pairSum = num + pairNum
                    if pairSum % 2 == 0:
                        if pairSum > maxSum:
                            maxSum = pairSum
                            bestPair = (num, pairNum)
            if digits not in seen:
                seen[digits] = [num]
return bestPair

nums = [51, 71, 17, 42] print(maxSum(nums)) # (51, 71)

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