Leetcode Problem 2815. Max Pair Sum in an Array

2815. Max Pair Sum in an Array

Leetcode Solutions

Using HashMap to Group Numbers by Maximum Digit

  1. Initialize a HashMap to store lists of numbers grouped by their maximum digit.
  2. Iterate through the array nums: a. For each number, convert it to a string and find the maximum digit. b. Add the number to the corresponding list in the HashMap using the maximum digit as the key.
  3. Initialize a variable maxSum to store the maximum pair sum found, initially set to -1.
  4. Iterate through the HashMap: a. For each key (maximum digit), sort the list of numbers in descending order. b. If the list contains at least two numbers, calculate the sum of the first two numbers. c. Update maxSum with the maximum of its current value and the calculated sum.
  5. Return maxSum if it's greater than -1, otherwise return -1.
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Brute Force Pairwise Comparison

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