Python: Maximum product of two numbers among all pairs in a list

Last update on April 21 2025 13:04:07 (UTC/GMT +8 hours)

24. Find Two Numbers with Maximum Product in a List Using a Set

Write a Python program to find the two numbers whose product is maximum among all the pairs in a given list of numbers. Use the Python set.

Sample Solution:

Python Code:

# Define a function 'max_product' that takes a list of integers 'nums' as input.
def max_product(nums):
    # Create a set 'nums_set' to efficiently check for unique numbers in the input list.
    nums_set = set(nums)
    
    # Initialize 'max_product' to negative infinity and 'max_num1' and 'max_num2' to None.
    max_product = float('-inf')
    max_num1 = None
    max_num2 = None
    
    # Iterate over the unique numbers in 'nums_set'.
    for n1 in nums_set:
        for n2 in nums_set:
            # Check if 'n1' and 'n2' are distinct and their product is greater than 'max_product'.
            if n1 != n2 and n1 * n2 > max_product:
                # Update 'max_product' with the new maximum product value.
                max_product = n1 * n2
                # Store the numbers that produced the maximum product in 'max_num1' and 'max_num2'.
                max_num1 = n1
                max_num2 = n2
    
    # Return a tuple containing the two numbers that produced the maximum product.
    return (max_num1, max_num2)

# Define a list of integers 'nums' for testing.
nums = [1, 2, 3, 4, 5, 6, 7, 8, 9]
print("Original list of integers:")
print(nums)

# Call the 'max_product' function and print the result for the list of integers.
print("Maximum product of two numbers among all pairs in the said list:")
print(max_product(nums))

# Repeat the process for a different set of integers.
nums = [1, -2, -3, 4, 5, -6, 7, -8, 9]
print("\nOriginal list of integers:")
print(nums)
print("Maximum product of two numbers among all pairs in the said list:")
print(max_product(nums))

Sample Output:

Original list of integers:
[1, 2, 3, 4, 5, 6, 7, 8, 9]
Maximum product of two numbers among all pairs in the said list:
(8, 9)

Original list of integers:
[1, -2, -3, 4, 5, -6, 7, -8, 9]
Maximum product of two numbers among all pairs in the said list:
(7, 9)

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to find the pair of distinct numbers in a list with the maximum product using set operations to remove duplicates.
Write a Python program to iterate over unique elements of a list and compute the maximum product from all possible pairs.
Write a Python program to use itertools.combinations on a set derived from the list to find the maximum product pair.
Write a Python program to implement a function that returns the pair of numbers with the maximum product after filtering out duplicates using a set.

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