Rotate Image

leetcode 48

You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

You have to rotate the image in place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

To solve the question we can first reverse the matrix, which will give us the following:

matrix.reverse()

After we reverse the matrix, we can see that we still need to exchange 4 with 8, 9 with 1, 6 with 2. We can do that by looping through the matrix to exchange the element:

for(let i=0;i<matrix.length;i++){
   for(let j=i;j<matrix[i].length;j++){
      let temp = matrix[i][j]
      matrix[i][j] = matrix[j][i]
      matrix[j][i] = temp
    }
}

This will get us:

And, that’s it!

The final result:

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

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