Maximum Product from List of Integers in Python

The challenge

Given an array of integers, Find the maximum product obtained from multiplying 2 adjacent numbers in the array.

Notes

  • Array/list size is at least 2.
  • Array/list numbers could be a mixture of positives, negatives also zeroes .

Input >Output Examples

adjacentElementsProduct([1, 2, 3]); ==> return 6
Code language: PHP (php)

Explanation:

The maximum product is obtained from multiplying 2 * 3 = 6, and they’re adjacent numbers in the array.

adjacentElementsProduct([9, 5, 10, 2, 24, -1, -48]); ==> return 50
Code language: PHP (php)

Explanation:

Max product obtained from multiplying 5 * 10 = 50 .

adjacentElementsProduct([-23, 4, -5, 99, -27, 329, -2, 7, -921]) ==> return -14
Code language: PHP (php)

Explanation:

The maximum product obtained from multiplying -2 * 7 = -14, and they’re adjacent numbers in the array.

The solution in Python code

Option 1:

def adjacent_element_product(array): return max( a*b for a, b in zip(array, array[1:]) )
Code language: Python (python)

Option 2:

def adjacent_element_product(arr): product = [arr[i]*arr[i+1] for i in range(len(arr)-1)] return max(product)
Code language: Python (python)

Option 3:

def adjacent_element_product(array): max = array[0]*array[1]; for i in range(1,len(array)-1): temp = array[i]*array[i+1] if max < temp: max = temp return max
Code language: Python (python)

Test cases to validate our solution

import test from solution import adjacent_element_product @test.describe("Fixed Tests") def fixed_tests(): @test.it("Positive numbers") def _(): test.assert_equals(adjacent_element_product([5, 8]), 40) test.assert_equals(adjacent_element_product([1, 2, 3]), 6) test.assert_equals(adjacent_element_product([1, 5, 10, 9]), 90) test.assert_equals(adjacent_element_product([4, 12, 3, 1, 5]), 48) test.assert_equals(adjacent_element_product([5, 1, 2, 3, 1, 4]), 6) @test.it("Both positive and negative values") def _(): test.assert_equals(adjacent_element_product([3, 6, -2, -5, 7, 3]), 21) test.assert_equals(adjacent_element_product([9, 5, 10, 2, 24, -1, -48]), 50) test.assert_equals(adjacent_element_product([5, 6, -4, 2, 3, 2, -23]), 30) test.assert_equals(adjacent_element_product([-23, 4, -5, 99, -27, 329, -2, 7, -921]), -14) test.assert_equals(adjacent_element_product([5, 1, 2, 3, 1, 4]), 6) @test.it("Contains zeroes") def _(): test.assert_equals(adjacent_element_product([1, 0, 1, 0, 1000]), 0) test.assert_equals(adjacent_element_product([1, 2, 3, 0]), 6)
Code language: Python (python)
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