238. Product of Array Except Self

Problem

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.

Solution

First attempt : (Can be optimized further)

var productExceptSelf = function(nums) {
    var output = [];
    var leftMult = 1; 
    var rightMult = 1;
    for(let i =0; i<nums.length;i++){
        output[i] = rightMult;
        rightMult = rightMult * nums[i];
    }
    console.log(output)
    for(let i = nums.length-1; i >=0; i--){
        output[i] = output[i]*leftMult;
        leftMult = leftMult * nums[i]
        
    }
   console.log(output)
    return output;
};