# Using a Dictionary with a Medium Level LeetCode: Find the Duplicate Number

*In this series, I will explain my thought process of figuring out one way to solve a particular LeetCode problem and then provide the JavaScript code.*

287. Find the Duplicate Number

The objective is to return whatever number is the **repeated number** in an array. We can assume that there will always be one.

An example test case:

**Input:** nums = [1,3,4,2,2]

**Output:** 2

Here is my initial thought process for breaking the problem down.

By using a **dictionary**, or a **hash**, we can keep track of the number of times a particular number is found.

In the last line, we are grabbing the key from the dictionary and returning it. However, we need to narrow it down to whichever key has a **value that is greater than 1**.

Of course, there are many ways to solve a problem, so feel free to share your thoughts in the comments below!

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