. Day 6 - Challenge 1 - Rotating a 2D Matrix in Place Skip to main content

Day 6 - Challenge 1 - Rotating a 2D Matrix in Place

Rotating a 2D Matrix in Place: A JavaScript Solution

Introduction: 

Rotating a 2D matrix by 90 degrees clockwise is a classic algorithmic problem that challenges your ability to manipulate arrays and indexes efficiently. In this blog post, we will explore an elegant solution to this problem using JavaScript, without requiring any extra space. We'll break down the problem, outline the approach, and provide a step-by-step implementation.

Problem Statement: 

Given a 2D matrix represented as an array of arrays, your task is to rotate the matrix by 90 degrees clockwise in-place.

Approach: 

The key idea behind rotating a matrix in-place is to perform a series of cyclic swaps of elements. We'll start by working on the outermost layer of the matrix and move towards the inner layers. For each layer, we'll perform a cyclic swap of four elements in a clockwise manner until the entire matrix is rotated.

Implementation in JavaScript: 

Let's dive into the JavaScript code that accomplishes this task:


function rotateMatrix(matrix) {
    const n = matrix.length;

    // Iterate through layers
    for (let layer = 0; layer < Math.floor(n / 2); layer++) {
        const first = layer;
        const last = n - 1 - layer;

        // Iterate within the current layer
        for (let i = first; i < last; i++) {
            const offset = i - first;
            const top = matrix[first][i]; // Save top element

            // Left to top
            matrix[first][i] = matrix[last - offset][first];

            // Bottom to left
            matrix[last - offset][first] = matrix[last][last - offset];

            // Right to bottom
            matrix[last][last - offset] = matrix[i][last];

            // Top to right
            matrix[i][last] = top; // Assign saved top to right
        }
    }
}

// Example usage
const matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
];

rotateMatrix(matrix);

console.log(matrix); // The rotated matrix will be printed here

Conclusion: 

Rotating a 2D matrix by 90 degrees clockwise without using extra space is a challenging problem that can be efficiently solved using cyclic swaps. The provided JavaScript solution demonstrates a step-by-step approach to achieve the rotation in-place. Understanding this algorithmic technique can be helpful not only for solving similar array manipulation problems but also for strengthening your programming skills overall.

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

Other Challenges:

  1. Day 3 Challenges
  2. Day 4 Challenges
  3. Day 5 Challenges

 

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