0238.ProductOfArrayExceptSelf.md

238. Product of Array Except Self

LeetCode Problem Link

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 <= $10^5$
• -30 <= nums[i] <= 30
• The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.

Solution

JavaScript

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

    for(let i = 1; i < nums.length; i++){
        result[i] = result[i - 1] * nums[i - 1];
    }

    for(let i = nums.length - 1; i >= 0; i--){
        result[i] = result[i] * rightProduct;
        rightProduct *= nums[i];
    }

    return result;
};