48. Rotate Image

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.

 

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]]

Example 3:

Input: matrix = [[1]]
Output: [[1]]

Example 4:

Input: matrix = [[1,2],[3,4]]
Output: [[3,1],[4,2]]

 

Constraints:

  • matrix.length == n
  • matrix[i].length == n
  • 1 <= n <= 20
  • -1000 <= matrix[i][j] <= 1000

Rust Solution

struct Solution;

impl Solution {
    fn rotate(matrix: &mut Vec<Vec<i32>>) {
        matrix.reverse();
        let n = matrix.len();
        for i in 0..n {
            for j in i + 1..n {
                let a = matrix[i][j];
                let b = matrix[j][i];
                matrix[i][j] = b;
                matrix[j][i] = a;
            }
        }
    }
}

#[test]
fn test() {
    let mut matrix: Vec<Vec<i32>> = vec_vec_i32![[1, 2, 3], [4, 5, 6], [7, 8, 9]];
    let res: Vec<Vec<i32>> = vec_vec_i32![[7, 4, 1], [8, 5, 2], [9, 6, 3]];
    Solution::rotate(&mut matrix);
    assert_eq!(matrix, res);
}

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