LeetCode Challenge: 48. Rotate Image - JavaScript Solution 🚀

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The 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 = [[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]]

- JavaScript Solution

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