Contains Duplicate

Problem

https://leetcode.com/problems/contains-duplicate/

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

Example 1:

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

Output: true

Explanation:

The element 1 occurs at the indices 0 and 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

Constraints:

• 1 <= nums.length <= 10:sup:`5`

• -10:sup:`9`<= nums[i] <= 10:sup:`9`

Pattern

Array, Hash Table, Sorting

Approaches

Hash Set

Code

def containsDuplicate(nums: list[int]) -> bool:
    """Return whether any value appears at least twice in ``nums``."""
    seen: set[int] = set()
    for n in nums:
        if n in seen:
            return True
        seen.add(n)
    return False

Test

>>> from contains_duplicate__hash_set import containsDuplicate
>>> containsDuplicate([1, 2, 3, 1])
True
>>> containsDuplicate([1, 2, 3, 4])
False
>>> containsDuplicate([1, 1, 1, 3, 3, 4, 3, 2, 4, 2])
True

contains_duplicate__hash_set.containsDuplicate(nums: list[int]) → bool

Return whether any value appears at least twice in nums.