N-Repeated Element in Size 2N Array

Problem Description

You are given an integer array nums with the following properties:

• nums.length == 2 * n.
• nums contains n + 1 unique elements.
• Exactly one element of nums is repeated n times.

Return the element that is repeated n times.

Key Insights

• The input array has a length of 2n, meaning it contains twice as many elements as the unique elements.
• Since there are n + 1 unique elements and one of them is repeated n times, we can identify the repeated element by counting occurrences.
• A hash table (or dictionary) can be effectively used to track the counts of each element in nums.

Space and Time Complexity

Time Complexity: O(n)
Space Complexity: O(n)

Solution

To solve this problem, we can utilize a hash table (or dictionary) to count the occurrences of each element in the input array nums. As we iterate through the array, we will increment the count for each element we encounter. Once we find an element with a count of n, we return that element as it is the repeated element.

Code Solutions