LeetCode-in-All

238. Product of Array Except Self

Medium

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:

Follow up: Can you solve the problem in O(1) extra space complexity? (The output array does not count as extra space for space complexity analysis.)

Solution

object Solution {
    def productExceptSelf(nums: Array[Int]): Array[Int] = {
        var product = 1
        val ans = new Array[Int](nums.length)

        for (num <- nums) {
            product = product * num
        }

        for (i <- nums.indices) {
            if (nums(i) != 0) {
                ans(i) = product / nums(i)
            } else {
                var p = 1
                for (j <- nums.indices) {
                    if (j != i) {
                        p = p * nums(j)
                    }
                }
                ans(i) = p
            }
        }

        ans
    }
}