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Contains Duplicate

Given an integer array nums, return True if any value appears at least twice in the array, and False if every element is distinct.

Input:

1,2,3,1

Output:

True

Reasoning:

We start by iterating over the input array: [1, 2, 3, 1]
As we iterate, we keep track of the elements we've seen so far
When we encounter the second 1, we realize it's a duplicate, since we've seen it before: $1 \in [1, 2, 3]$
The presence of a duplicate immediately returns True, indicating that the array contains at least one value that appears twice
The final output is therefore: True

Editor

Python 3.13.1

0/0

Run code to see test results.