Python: Find numbers that are adjacent to a prime number in the list, sorted without duplicates

Last update on May 30 2025 11:50:11 (UTC/GMT +8 hours)

Numbers Adjacent to Primes

Prime number: A number that is divisible only by itself and 1 (e.g. 2, 3, 5, 7, 11).
Write a Python program to find a list of all numbers that are adjacent to a prime number in the list, sorted without duplicates.

Input:
[2, 17, 16, 0, 6, 4, 5]
Output:
[2, 4, 6, 16, 17]

Input:
[1, 2, 19, 16, 6, 4, 10]
Output:
[1, 2, 16, 19]

Input:
[1, 2, 3, 5, 1, 16, 7, 11, 4]
Output:
[1, 2, 3, 4, 5, 7, 11, 16]

Visual Presentation:

Sample Solution:

Python Code:

# Define a function named 'test' that takes a list of numbers as input
def test(nums):
    # Use a set comprehension to create a set of numbers that are adjacent to a prime number in the list
    return sorted({
        n for i, n in enumerate(nums)
        if (i > 0 and prime(nums[i - 1])) or (i < len(nums) - 1 and prime(nums[i + 1]))
    })

# Define a function named 'prime' that checks if a given number is prime
def prime(m):
    # Check if the number is greater than 0 and is divisible by any number in the range (2, m - 1)
    return all(m % i for i in range(2, m - 1))

# Set a list of numbers
nums = [2, 17, 16, 0, 6, 4, 5]
# Print a message indicating the original list of numbers
print("Original list of numbers:")
# Print the original list of numbers
print(nums)
# Print a message indicating numbers adjacent to a prime number, sorted without duplicates
print("Numbers that are adjacent to a prime number in the said list, sorted without duplicates:")
# Print the result of the 'test' function applied to the numbers
print(test(nums))

# Set another list of numbers
nums = [1, 2, 19, 16, 6, 4, 10]
# Print a message indicating the original list of numbers
print("\nOriginal list of numbers:")
# Print the original list of numbers
print(nums)
# Print a message indicating numbers adjacent to a prime number, sorted without duplicates
print("Numbers that are adjacent to a prime number in the said list, sorted without duplicates:")
# Print the result of the 'test' function applied to the numbers
print(test(nums))

# Set yet another list of numbers
nums = [1, 2, 3, 5, 1, 16, 7, 11, 4]
# Print a message indicating the original list of numbers
print("\nOriginal list of numbers:")
# Print the original list of numbers
print(nums)
# Print a message indicating numbers adjacent to a prime number, sorted without duplicates
print("Numbers that are adjacent to a prime number in the said list, sorted without duplicates:")
# Print the result of the 'test' function applied to the numbers
print(test(nums))

Sample Output:

Original list of numbers:
[2, 17, 16, 0, 6, 4, 5]
Numbers that are adjacent to a prime number in the said list, sorted without duplicates:
[2, 4, 16, 17]

Original list of numbers:
[1, 2, 19, 16, 6, 4, 10]
Numbers that are adjacent to a prime number in the said list, sorted without duplicates:
[1, 2, 16, 19]

Original list of numbers:
[1, 2, 3, 5, 1, 16, 7, 11, 4]
Numbers that are adjacent to a prime number in the said list, sorted without duplicates:
[1, 2, 3, 4, 5, 7, 11, 16]

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Python program to scan a list of numbers and return those numbers which are immediately adjacent to a prime number.
• Write a Python program to check for each number if its preceding or succeeding number is prime and collect unique results.
• Write a Python program to use a helper function that determines if a neighbor is prime, then filter the list accordingly.
• Write a Python program to implement a one-pass algorithm that returns numbers with at least one prime neighbor, ensuring no duplicates.

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Python Code Editor :

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