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LeetCode solutions

4100. Complete Prime Number

My accepted Python solution to LeetCode problem 4100, Complete Prime Number, running in 0ms.

  • Difficulty: Medium
  • Python
  • Runtime 0ms
  • Memory 17.6MB

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 17.6MB, accepted 2025-12-29.

python
class Solution:
    def completePrime(self, num: int) -> bool:
        def is_prime(n):
            if n < 2:
                return False
            if n == 2:
                return True
            if n % 2 == 0:
                return False
            for i in range(3, int(n**0.5) + 1, 2):
                if n % i == 0:
                    return False
            return True
        
        s = str(num)
        n = len(s)
        
        # Check all prefixes (first k digits)
        for k in range(1, n + 1):
            prefix = int(s[:k])
            if not is_prime(prefix):
                return False
        
        # Check all suffixes (last k digits)
        for k in range(1, n + 1):
            suffix = int(s[-k:])
            if not is_prime(suffix):
                return False
        
        return True

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