Python: Reorder numbers in increasing/decreasing order based on whether the first plus last element is even/odd

Last update on May 30 2025 11:49:06 (UTC/GMT +8 hours)

Reorder Numbers Based on Sum

Write a Python program to reorder numbers from a given array in increasing/decreasing order based on whether the first plus last element is odd/even.

Input: 
[3, 7, 4]
Output:
[3, 4, 7]

Input:  
[2, 7, 4]
Output:
[7, 4, 2]

Input: 
[1, 5, 6, 7, 4, 2, 8] 
Output:
[1, 2, 4, 5, 6, 7, 8]

Input:  
[1, 5, 6, 7, 4, 2, 9]
Output:
[9, 7, 6, 5, 4, 2, 1]

Visual Presentation:

Sample Solution:

Python Code:

# License: https://bit.ly/3oLErEI

# Define a function named 'test' that takes a list of numbers as input
def test(nums):
    # Use the sorted function to reorder the numbers based on whether the sum of the first and last element is odd/even
    return sorted(nums, reverse=(False if (nums[0] + nums[-1]) % 2 else True))

# Print a message indicating the purpose of the code
print("Reorder numbers of a given array in increasing/decreasing order based on whether the first plus last element is odd/even.")

# Example 1
nums1 = [3, 7, 4]
print("\nList of numbers:", nums1)
print("Result:")
print(test(nums1))

# Example 2
nums2 = [2, 7, 4]
print("\nList of numbers:", nums2)
print("Result:")
print(test(nums2))

# Example 3
nums3 = [1, 5, 6, 7, 4, 2, 8]
print("\nList of numbers:", nums3)
print("Result:")
print(test(nums3))

# Example 4
nums4 = [1, 5, 6, 7, 4, 2, 9]
print("\nList of numbers:", nums4)
print("Result:")
print(test(nums4))

Sample Output:

Reorder numbers of a give array in increasing/decreasing order based on whether the first plus last element is odd/even.:

List of numbers: [3, 7, 4]
Result:
[3, 4, 7]

List of numbers: [2, 7, 4]
Result:
[7, 4, 2]

List of numbers: [1, 5, 6, 7, 4, 2, 8]
Result:
[1, 2, 4, 5, 6, 7, 8]

List of numbers: [1, 5, 6, 7, 4, 2, 9]
Result:
[9, 7, 6, 5, 4, 2, 1]

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Python program to sort a list in increasing order if the sum of the first and last elements is odd, otherwise in decreasing order.
• Write a Python program to reorder an array by checking the parity of the sum of its first and last elements and sorting accordingly.
• Write a Python program to use conditional logic to sort a list ascendingly or descendingly based on whether the first plus last element is odd or even.
• Write a Python program to implement a function that sorts the list in two different ways determined by the sum of its outer elements.

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Python Code Editor :

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