Merge pull request neetcode-gh#1579 from benmarg/productExceptSelf

Update: 238-Product-Of-Array-Except-Self.js

javascript/238-Product-of-Array-Except-Self.js

@@ -5,67 +5,19 @@
  * @param {number[]} nums
  * @return {number[]}
  */
-var productExceptSelf = (nums) => {
- const products = 2;
- const [ leftProduct, rightProduct ] = getProducts(products, nums);
-
- carryForward(nums, leftProduct); /* Time O(N) | Space O(N) */
- carryBackward(nums, rightProduct); /* Time O(N) | Space O(N) */
-
- return combineProducts(nums, leftProduct, rightProduct); /* Time O(N) | Ignore Auxillary Space O(N) */
-}
-
-const getProducts = (products, nums) => new Array(products).fill()
- .map(() => new Array(nums.length).fill(1));
-
-var carryForward = (nums, leftProduct) => {
- for (let index = 1; index < nums.length; index++) {/* Time O(N) */
- leftProduct[index] = nums[index - 1] * leftProduct[index - 1];/* Space O(N) */
+ function productExceptSelf(nums) {
+ const result = [];
+ let prefix = 1;
+ let postfix = 1;
+
+ for (let i = 0; i < nums.length; i++) {
+ result[i] = prefix;
+ prefix *= nums[i];
  }
-}
-
-var carryBackward = (nums, rightProduct) => {
- for (let index = (nums.length - 2); 0 <= index; index--) {/* Time O(N) */
- rightProduct[index] = nums[index + 1] * rightProduct[index + 1];/* Space O(N) */
+ for (let i = nums.length - 2; i >= 0; i--) {
+ postfix *= nums[i + 1];
+ result[i] *= postfix;
  }
-}
-
-const combineProducts = (nums, leftProduct, rightProduct) => {
- const products = new Array(nums.length).fill(1);/* Ignore Auxillary Space O(N) */
-
- for (let index = 0; index < nums.length; index++) {/* Time O(N) */
- products[index] = leftProduct[index] * rightProduct[index];/* Ignore Auxillary Space O(N) */
- }
-
- return products;
-}
-
-/**
- * Array - Ignore Auxillary Space
- * Time O(N) | Space O(1)
- * https://leetcode.com/problems/product-of-array-except-self/
- * @param {number[]} nums
- * @return {number[]}
- */
-var productExceptSelf = (nums) => {
- const products = new Array(nums.length).fill(1);/* Ignore Auxillary Space O(N) */
-
- carryForward(nums, products); /* Time O(N) | Ignore Auxillary Space O(N) */
- carryBackward(nums, products);/* Time O(N) | Ignore Auxillary Space O(N) */
-
- return products;
-};
-
-var carryForward = (nums, products, product = 1) => {
- for (let index = 0; index < nums.length; index++) {/* Time O(N) */
- products[index] = product; /* Ignore Auxillary Space O(N) */
- product *= nums[index];
- }
-}
-
-var carryBackward = (nums, products, product = 1) => {
- for (let index = (nums.length - 1); 0 <= index; index--) {/* Time O(N) */
- products[index] *= product; /* Ignore Auxillary Space O(N) */
- product *= nums[index];
- }
-}
+
+ return result;
+};