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LeetCode solutions

1468. Check If N and Its Double Exist

My accepted Python solution to LeetCode problem 1468, Check If N and Its Double Exist, running in 0ms.

  • Difficulty: Easy
  • Python
  • Runtime 0ms
  • Memory 17.4MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

Python

Accepted on LeetCode — runtime 0ms, memory 17.4MB, accepted 2025-12-29.

python
class Solution:
    def checkIfExist(self, arr: List[int]) -> bool:
        # Use hash set for O(n) lookup
        # Time: O(n), Space: O(n)
        seen = set()
        
        for num in arr:
            if num * 2 in seen or (num % 2 == 0 and num // 2 in seen):
                return True
            seen.add(num)
        
        return False

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