Loop Array Hash Map Counting Prefix Sum
Intermediate Level

Implement the productArrayExceptSelf method that returns an array where each value is the product of all other values.

The input contains an integer array nums and its length size. Your task is to return a new array where each index contains the product of all elements except the value at that same index.

For example, for [1,2,3,4], the result is [24,12,8,6] because each position multiplies all other values except itself.

Example 1
Input:
nums (int[]) = [1,2,3,4]
size (int) = 4
Return:
(int[]) [24,12,8,6]
Example 2
Input:
nums (int[]) = [-1,1,0,-3,3]
size (int) = 5
Return:
(int[]) [0,0,9,0,0]
Example 3
Input:
nums (int[]) = [2,3]
size (int) = 2
Return:
(int[]) [3,2]

Use prefix and suffix products so that each answer can be calculated without dividing.

First pass from left to right and store the product of all elements before each index. Then pass from right to left and multiply each position by the product of all elements after that index.

This also handles arrays containing zero because the method does not rely on division.

Pseudocode:

function productArrayExceptSelf(nums, size):
    answer = array of size values filled with 1
    prefix = 1
    for i from 0 to size - 1:
        answer[i] = prefix
        prefix = prefix * nums[i]
    suffix = 1
    for i from size - 1 down to 0:
        answer[i] = answer[i] * suffix
        suffix = suffix * nums[i]
    return answer
Run your code to see the result.