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:

• 2 <= nums.length <= 105
• -30 <= nums[i] <= 30
• The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.

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

/**
 * @param {number[]} nums
 * @return {number[]}
 */
var productExceptSelf = function(nums) {
    const res = new Array(nums.length).fill(1)

    let prefixProduct = 1
    for (let i = 0; i < nums.length; i++) {
        res[i] = prefixProduct
        prefixProduct *= nums[i]
    }

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

    return res
};

export { productExceptSelf }

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