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

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adjacentElementsProduct([1, 2, 3]); ==> return 6

Explanation:

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

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adjacentElementsProduct([9, 5, 10, 2, 24, -1, -48]); ==> return 50

Explanation:

Max product obtained from multiplying 5 * 10 = 50 .

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

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:

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

Option 2:

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

Option 3:

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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

Test cases to validate our solution

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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)