Leetcode problem solution-interview question 01.07. Rotation matrix

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Title description:

Give you an image represented by an N × N matrix, where each pixel is 4 bytes in size. Please design an algorithm to rotate the image by 90 degrees.

Can it be done without taking up additional memory space?

Example 1:

Given matrix =
[
[1,2,3],
[4,5,6],
[7,8,9]
],
rotate the input matrix in place to make it become:
[
[7,4,1],
[8,5,2],
[9,6,3]
]

Example 2:

Given matrix =
[
[5, 1, 9,11],
[2, 4, 8,10],
[13, 3, 6, 7],
[15,14,12,16]
],
rotate input in place Matrix so that it becomes:
[
[15,13, ​​2, 5],
[14, 3, 4, 1],
[12, 6, 8, 9],
[16, 7,10,11]
]

In-situ modification

  Find the law and add a little impression of college linear algebra. . .

1. Matrix transpose (swap elements up and down along the main diagonal);
2. Each line is flipped left and right by the center point.

Code

class Solution {
    
    
public:
    void rotate(vector<vector<int>>& matrix) {
    
    
        int len = matrix.size();
        for(int i = 0; i < len - 1; i++)
            for(int j = i + 1; j < len; j++)
                swap(matrix[i][j], matrix[j][i]);
            
        int mid = len / 2;
        for(int i = 0; i < len; i++){
    
    
            for(int j = 0; j < mid; j++){
    
    
                swap(matrix[i][j], matrix[i][len - 1 - j]);
            }
        }
        
        return;
    }
};

If there are mistakes or not rigorous, please correct me, thank you very much.
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