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]]
Constraints:
- n == matrix.length == matrix[i].length
- 1 <= n <= 20
- -1000 <= matrix[i][j] <= 1000
From: LeetCode
Link: 48. Rotate Image
Solution:
Ideas:
To rotate a matrix by 90 degrees clockwise in place, we can follow a two-step process:
-
Transpose the Matrix: The transpose of a matrix is obtained by swapping rows and columns. This means
matrix[i][j] will become matrix[j][i]. -
Reverse the Rows: Reverse each row of the transposed matrix.文章来源:https://www.toymoban.com/news/detail-630395.html
Following these steps will give us the rotated matrix.文章来源地址https://www.toymoban.com/news/detail-630395.html
Code:
void rotate(int** matrix, int matrixSize, int* matrixColSize) {
// Transpose the matrix
for (int i = 0; i < matrixSize; i++) {
for (int j = i; j < matrixSize; j++) {
int temp = matrix[i][j];
matrix[i][j] = matrix[j][i];
matrix[j][i] = temp;
}
}
// Reverse each row
for (int i = 0; i < matrixSize; i++) {
for (int j = 0, k = matrixSize - 1; j < k; j++, k--) {
int temp = matrix[i][j];
matrix[i][j] = matrix[i][k];
matrix[i][k] = temp;
}
}
}
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