ProductArrayExceptSelf.js

/*
Given an integer array nums, return an array answer such that answer[i] is equal to the product of all the 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 operation.

 

Example 1:

Input: nums = [1,2,3,4]
Output: [24,12,8,6]
Example 2:

Input: nums = [-1,1,0,-3,3]
Output: [0,0,9,0,0]
 

Constraints:

2 <= nums.length <= 105
-30 <= nums[i] <= 30
The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.
 

Follow up: Can you solve the problem in O(1) extra space complexity? (The output array does not count as extra space for space complexity analysis.)
*/


var productExceptSelf = function(nums) {
    const n = nums.length;
    const output = [];
  
    // Calculate the product of all elements before each index
    let leftProduct = 1;
    for (let i = 0; i < n; i++) {
      output[i] = leftProduct;
      leftProduct *= nums[i];
    }
  
    // Calculate the product of all elements after each index and multiply it with the product before each index
    let rightProduct = 1;
    for (let i = n - 1; i >= 0; i--) {
      output[i] *= rightProduct;
      rightProduct *= nums[i];
    }
  
    return output;
  };