rotateMatrix function

void rotateMatrix(List<List<int>> matrix)

Rotates a square matrix (n x n) 90 degrees clockwise in-place.

This function modifies the input matrix directly.

Time Complexity: O(n^2), where n is the dimension of the matrix. Space Complexity: O(1)

Example:

var matrix = [
  [1, 2, 3],
  [4, 5, 6],
  [7, 8, 9],
];
rotateMatrix(matrix);
print(matrix); // Outputs: [[7,4,1],[8,5,2],[9,6,3]]

Implementation

void rotateMatrix(List<List<int>> matrix) {
  final n = matrix.length;
  for (int i = 0; i < n ~/ 2; i++) {
    for (int j = i; j < n - i - 1; j++) {
      int temp = matrix[i][j];
      matrix[i][j] = matrix[n - j - 1][i];
      matrix[n - j - 1][i] = matrix[n - i - 1][n - j - 1];
      matrix[n - i - 1][n - j - 1] = matrix[j][n - i - 1];
      matrix[j][n - i - 1] = temp;
    }
  }
}