NRepeated Element in Size 2N Array
You have an integer array nums
of length 2 * n
, which consists of n + 1
unique elements. Among these elements, one of them is repeated exactly n
times. You are required to find and return that repeated element.
Approach
A straightforward approach to solving this problem is to use a dictionary or hash table to count the occurrences of each element. Since one element is repeated exactly n
times, the element with a count of n
will be the answer.
Here’s a stepbystep guide:
Create a Dictionary: Initialize an empty dictionary to keep track of the count of each number in the array.
Count the Occurrences: Iterate through the array, and for each number, increment its count in the dictionary.
Find the Repeated Element: Iterate through the dictionary, and return the number that has a count of
n
.
Code


Key Takeaways
 We are looking for an element that is repeated exactly
n
times in an array of length2 * n
.  Using a dictionary to count occurrences allows us to easily find the element that meets the given condition.
 This approach is simple to understand and implement, making use of basic data structures and iteration.