ProductOfArrayExceptSelf.go

// Source : https://leetcode.com/problems/product-of-array-except-self/description/
// Author : Hamza Mogni
// Date   : 2023-05-08

/*****************************************************************************************************
 *
 * 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.
 *
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 * count as extra space for space complexity analysis.)
 ******************************************************************************************************/

package main

import "fmt"

func main() {
	fmt.Println(productExceptSelf([]int{1, 2, 3, 4}))

}

func productExceptSelf(nums []int) []int {
	result := make([]int, len(nums))

	prefix := 1
	for i, num := range nums {
		result[i] = prefix
		prefix *= num
	}

	postfix := 1
	for i := len(result) - 1; i >= 0; i-- {
		result[i] *= postfix
		postfix *= nums[i]
	}

	return result
}