Problem Description
You are given a 0-indexed integer array nums. In one operation, you may choose two integers in nums that are equal and remove both integers from nums, forming a pair. The operation is done on nums as many times as possible. Return a 0-indexed integer array answer of size 2 where answer[0] is the number of pairs that are formed and answer[1] is the number of leftover integers in nums after doing the operation as many times as possible.
Key Insights
- Pairs can only be formed using equal integers.
- Counting the occurrences of each integer allows us to determine how many pairs can be formed.
- Any leftover integers will be the total count of integers minus twice the number of pairs formed.
Space and Time Complexity
Time Complexity: O(n), where n is the length of the array nums, because we need to iterate through the array to count occurrences.
Space Complexity: O(1), since the maximum number of unique integers is limited (0 to 100), we can use a fixed-size array for counting.
Solution
To solve the problem, we can use a counting approach. We'll maintain an array (or a hash table) to count the occurrences of each integer in nums. After counting, we can compute the number of pairs that can be formed by dividing the count of each integer by 2 and summing these values. The leftover integers will be calculated as the total number of integers minus twice the number of pairs formed.