LeetCode Challenge: 48. Rotate Image - JavaScript Solution 🚀

Top Interview 150

The Rotate Image problem involves rotating an n×n matrix by 90 degrees clockwise, in place. Let’s solve LeetCode 48: Rotate Image step by step.

🚀 Problem Description

Given an n×n matrix:

• Rotate the matrix in place by 90 degrees clockwise.
• In-place means modifying the original matrix without allocating extra space for another matrix.

💡 Examples

Example 1

Input: matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] Output: [[7, 4, 1], [8, 5, 2], [9, 6, 3]] 

Example 2

Input: matrix = [[5, 1, 9, 11], [2, 4, 8, 10], [13, 3, 6, 7], [15, 14, 12, 16]] Output: [[15, 13, 2, 5], [14, 3, 4, 1], [12, 6, 8, 9], [16, 7, 10, 11]] 

Constraints

• 1≤m,n≤10
• −100≤matrix[i][j]≤100

🏆 JavaScript Solution

We solve this problem in two steps:

1. Transpose the Matrix:

   • Swap elements symmetrically across the diagonal.

2. Reverse Each Row:

   • Reverse the order of elements in each row to achieve the rotation.

Implementation

var rotate = function(matrix) { const n = matrix.length; for (let i = 0; i < n; i++) { for (let j = i + 1; j < n; j++) { [matrix[i][j], matrix[j][i]] = [matrix[j][i], matrix[i][j]]; } } for (let i = 0; i < n; i++) { matrix[i].reverse(); } }; 

🔍 How It Works

1. Transpose the Matrix:
   • Swap matrix[i][j] with matrix[j][i] for all i<j.
   • This converts rows into columns.

Example:

Input: [[1, 2, 3], Transposed: [[1, 4, 7], [4, 5, 6], -> [2, 5, 8], [7, 8, 9]] [3, 6, 9]] 

1. Reverse Each Row:
   • Reverse the elements of each row to achieve the clockwise rotation.

Example:

Transposed: [[1, 4, 7], Rotated: [[7, 4, 1], [2, 5, 8], -> [8, 5, 2], [3, 6, 9]] [9, 6, 3]] 

🔑 Complexity Analysis

• Time Complexity:

  • Transposing the matrix takes O(n^2).
  • Reversing each row takes O(n^2).
  • Total: O(n^2)

• Space Complexity: O(1), as the rotation is done in place.

📋 Dry Run

Input: matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

Output: [[7, 4, 1], [8, 5, 2], [9, 6, 3]]

✨ Pro Tips for Interviews

1. Clarify Constraints:

   • Ensure the matrix is always square (n×n).

2. Highlight In-Place Operations:

   • Emphasize the efficiency of the transpose-and-reverse method.

3. Edge Cases:

   • Single-element matrix: [[1]].
   • 2×2 matrix: [[1, 2], [3, 4]].

📚 Learn More

Check out the full explanation and code walkthrough on my previous Dev.to post:
👉 Spiral Matrix - JavaScript Solution

What’s your preferred method to solve this problem? Let’s discuss! 🚀