Problem – Product of Array Except Self

https://leetcode.com/problems/

Given an array nums of n integers where n > 1,  return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].

Example:

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

Constraint: It’s guaranteed that the product of the elements of any prefix or suffix of the array (including the whole array) fits in a 32 bit integer.

Note: Please solve it without division and in O(n).

Follow up:
Could you solve it with constant space complexity? (The output array does not count as extra space for the purpose of space complexity analysis.)

Group Anagrams ES6 solution

#1 O(n^2) time complexity solution

/**
@param {number[]} nums
@return {number[]}
*/
var productExceptSelf = function(nums) {
let result = [];
result[nums.length - 1] = 1;
for(let i = nums.length - 2; i >= 0; i--){
result[i] = result[i + 1] * nums[i + 1];
}
let left = 1;
for(let i = 0; i < nums.length; i++){
result[i] = result[i] * left;
left = left * nums[i];
}
return result;
};
productExceptSelf([-1,-1,1,-1,-1,1,-1,-1, ………50K])

runtime 140ms

#2 O(n) time complexity solution

/**
@param {number[]} nums
@return {number[]}
*/
var productExceptSelf = function(nums) {
let result = [];
result[nums.length - 1] = 1;
for(let i = nums.length - 2; i >= 0; i--){
result[i] = result[i + 1] * nums[i + 1];
}
let left = 1;
for(let i = 0; i < nums.length; i++){
result[i] = result[i] * left;
left = left * nums[i];
}
return result;
};

runtime 84ms

Submission Output on LeetCode: