Contains Duplicate Python Solution with Tests

Tested Python solution for LeetCode 217 with 12 pytest cases. Generate a practice environment with lcpy.

LeetCode 217, Easy. Topics: Array, Hash Table, Sorting. View on LeetCode.

Generate this problem as a practice environment: tested reference solution, 12 parametrized pytest cases, and a playground notebook:

lcpy gen -n 217   # by problem number
lcpy gen -s contains_duplicate   # by problem name

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Problem

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.

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Examples

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

Explanation: The element 1 occurs at the indices 0 and 3.

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

Explanation: All elements are distinct.

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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Solution

Reference implementation from solution.py on GitHub, full suite in test_solution.py:

class Solution:
    # Time: O(n)
    # Space: O(n)
    def contains_duplicate(self, nums: list[int]) -> bool:
        seen = set()
        for num in nums:
            if num in seen:
                return True
            seen.add(num)
        return False

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Complexity

Time	Space
O(n)	O(n)

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Tags

Grind 75, Grind, Blind 75, NeetCode 150, NeetCode 250, NeetCode All.