Solve Product of Array Except Self Problem in 4 Easy Steps

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Introduction

Welcome back, visitors! In this article, we will delve into the Product of Array Except Self problem, a popular intermediate-level interview question often found on platforms like LeetCode. We will explore various approaches to solve this problem using different programming languages such as Python, Java, JavaScript, and C++. This guide will help you understand the concept thoroughly, making it easier to explain and implement during your interviews.

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What Is the Product of Array Except Self Problem?

The Product of Array Except Self problem is a common coding interview question and part of the Blind 75 list. It involves returning an array output such that output[i] is equal to the product of all elements of the input array except nums[i].

Example:

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

Understanding this problem enhances your algorithmic thinking and array manipulation skills. For more details, visit interviewspreparation.com.

Approaches to Solve the Problem

Optimized Approach Without Division

A more efficient way to solve this problem is to use two additional arrays (left and right) to store the product of all elements to the left and right of each index. This approach has a time complexity of O(n) and a space complexity of O(n).

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Python

def product_except_self(nums):
    n = len(nums)
    left = [1] * n
    right = [1] * n
    output = [1] * n

    for i in range(1, n):
        left[i] = left[i - 1] * nums[i - 1]

    for i in range(n - 2, -1, -1):
        right[i] = right[i + 1] * nums[i + 1]

    for i in range(n):
        output[i] = left[i] * right[i]

    return output

nums = [1, 2, 3, 4]
print(product_except_self(nums))

Conclusion

The Product of Array Except Self problem involves calculating an array where each element is the product of all other elements except the one at the current index. This guide covers both the brute force and optimized approaches to help you master this problem for coding interviews.