product-of-array-except-self.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.
 */

/**
 * @param {number[]} nums
 * @return {number[]}
 */
 var productExceptSelf = function(nums) {
    const arr = new Array(nums.length).fill(1);

    let prefix = 1;
    for (let i = 0; i < nums.length; i++) {
        arr[i] = prefix;
      prefix *= nums[i];
    }
  
    let postfix = 1;
    for (let i = nums.length - 1; i >= 0; i--) {
        arr[i] *= postfix;
      postfix *= nums[i];
    }
  
    return arr;

};