Product of Array Except Self

Write a function that returns an array where answer[i] is equal to the product of all elements of nums except nums[i]. The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer. You must write an algorithm that runs in O(n) time and without using the division operator.

How to Solve

Use two passes: first pass calculates left products (product of all elements to the left), second pass calculates right products (product of all elements to the right) and multiplies with left products. This avoids division and achieves O(n) time.

Code

const productExceptSelf = (nums: number[]): number[] => {
  // Your implementation here
};

Test Cases

Input 1

const nums1 = [1, 2, 3, 4];

Expected Output: [24, 12, 8, 6] (24 = 234, 12 = 134, 8 = 124, 6 = 123)

Input 2

const nums2 = [-1, 1, 0, -3, 3];

Expected Output: [0, 0, 9, 0, 0]

Input 3

const nums3 = [2, 3];

Expected Output: [3, 2]

Complexity

Time Complexity: O(n) - Two passes through the array, each taking O(n) time.

Space Complexity: O(1) - Output array doesn't count as extra space. We only use a few variables for the right product calculation.