Contains Duplicate

Given an integer array nums, return true if any value appears more than once in the array, otherwise return false.

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Example 1

**Input:** nums = [1, 2, 3, 1]
**Output:** true

Explanation: The element 1 appears at index 0 and index 3.

Example 2

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

Explanation: All elements are distinct.

Example 3

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

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Constraints

• 1 <= nums.length <= 10^5
• -10^9 <= nums[i] <= 10^9

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Hints

💡 Hint 1

Think about what data structure lets you check "have I seen this before?" in O(1) time.

💡 Hint 2

A HashSet stores unique values. If you try to add a value that's already there, you've found a duplicate.

💡 Hint 3

There's a one-liner approach: compare the length of the array vs the length of the set of the array.