You are given an n x n 2D matrix representing an image.
Rotate the image by 90 degrees (clockwise).
Follow up:
- Could you do this in-place?
C Solution:
void rotate(int** matrix, int matrixRowSize, int matrixColSize) {
int i, n = matrixRowSize;
for (i = 0; i < n / 2; i++) {
int j;
for (j = i; j < n - 1 - i; j++) {
int tmp = matrix[j][n - 1 - i];
matrix[j][n - 1 - i] = matrix[i][j];
matrix[i][j] = matrix[n - 1 - j][i];
matrix[n - 1 - j][i] = matrix[n - 1 - i][n - 1 - j];
matrix[n - 1 - i][n - 1 - j] = tmp;
}
}
}
Python Solution 1:
class Solution(object):
def rotate(self, matrix):
"""
:type matrix: List[List[int]]
:rtype: void Do not return anything, modify matrix in-place instead.
"""
N = len(matrix)
for i in range(N // 2):
for j in range(i, N - 1 - i):
matrix[i][j], matrix[j][N - 1 - i], matrix[N - 1 - i][N - 1 - j], matrix[N - 1 - j][i] = (
matrix[N - 1 - j][i], matrix[i][j], matrix[j][N - 1 - i], matrix[N - 1 - i][N - 1 - j]
)
Python Solution 2:
class Solution(object):
def rotate(self, matrix):
"""
:type matrix: List[List[int]]
:rtype: void Do not return anything, modify matrix in-place instead.
"""
N = len(matrix)
for i in range(N // 2):
for j in range(i, N - 1 - i):
matrix[i][j], matrix[j][~i], matrix[~i][~j], matrix[~j][i] = (
matrix[~j][i], matrix[i][j], matrix[j][~i], matrix[~i][~j]
)
Summary:
- The key point here is to find the right index.
- There is another way, maybe better, maybe worse.
LeetCode: 48. Rotate Image
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