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Day 9 - Challenge 1 - Product of Array Except Self

Solving the "Product of Array Except Self" Problem in JavaScript

Are you ready to dive into a common coding challenge that not only tests your programming skills but also sharpens your problem-solving mindset? If you're up for the challenge, let's tackle the "Product of Array Except Self" problem together using JavaScript. This problem requires us to return an array where each element at index i is the product of all the elements in the original array except the one at index i.

Understanding the Problem: 

Imagine you're given an array of integers, let's call it nums. Your task is to create a new array where the value at index i in this new array is the product of all the elements in nums, except the one at index i. In other words, you're calculating the product of all the elements to the left of nums[i] and the product of all the elements to the right of nums[i], and then multiplying these two products to get the final value at index i in the new array.

Approach: Two-Pass Technique 

To solve this problem efficiently, we'll use a two-pass technique. In the first pass, we'll calculate the product of all elements to the left of each index i, and in the second pass, we'll calculate the product of all elements to the right of each index i. By combining the results of these two passes, we'll obtain the desired output array.

Let's Dive into the Code:

function productExceptSelf(nums) {
  const n = nums.length;
  const result = new Array(n);

  // Calculate the product of all elements to the left of each element
  let leftProduct = 1;
  for (let i = 0; i < n; i++) {
    result[i] = leftProduct;
    leftProduct *= nums[i];
  }

  // Calculate the product of all elements to the right of each element
  let rightProduct = 1;
  for (let i = n - 1; i >= 0; i--) {
    result[i] *= rightProduct;
    rightProduct *= nums[i];
  }
  return result;
}
const inputArray = [1, 2, 3, 4];
const outputArray = productExceptSelf(inputArray);
console.log(outputArray); // Output: [24, 12, 8, 6]

Demo:

Product of Array Except Self


Explanation: 

In the first pass, we traverse the array from left to right while maintaining a running product of all elements to the left. This is then stored in the result array at each index i.

In the second pass, we traverse the array from right to left while maintaining a running product of all elements to the right. We update the result array at each index i by multiplying it with the corresponding value from the right pass.

Finally, the result array contains the product of all elements except the one at each index i, as desired.

Conclusion: 

By breaking down the problem into two passes and strategically calculating the product of elements to the left and right of each index, we've efficiently solved the "Product of Array Except Self" problem using JavaScript. This solution showcases how a well-thought-out approach can lead to an elegant solution for complex coding challenges. So, are you ready to take on more coding adventures? Happy coding!

Now write the same program in your favorite language in comment section. 

Other Challenges:

  1. Day 6 Challenges 
  2. Day 7 Challenges
  3. Day 8 Challenges

 

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