Finding the First Duplicate in an Array

Introduction to Finding the First Duplicate

This tutorial will guide you through creating a simple algorithm to find the first duplicate in an array of integers.

Step 1: Define the Problem and the Approach

We are given an array of integers and we need to find the first duplicate in the array. We will use a hash set to solve this problem.

Step 2: Initialize an Empty Hash Set

We will initialize an empty hash set to store the unique elements we have seen so far.

seen = set()

Step 3: Loop Through the Array and Check for Duplicates

We will loop through the array and check if each element is already in the hash set. If it is, we will return the element as the first duplicate.

for num in array:
    if num in seen:
        return num
    seen.add(num)

Step 4: Return None if No Duplicate is Found

If the loop ends without finding a duplicate, we will return None to indicate that there is no duplicate in the array.

return None

Example Use Case

Here's an example use case:

array = [2, 1, 3, 5, 3, 2]
seen = set()
for num in array:
    if num in seen:
        print(num)  # Output: 3
        break
    seen.add(num)