You are given an n x n 2D matrix representing an image.
Rotate the image by 90 degrees (clockwise).
Note:
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:
Given input matrix = [ [1,2,3], [4,5,6], [7,8,9] ], rotate the input matrix in-place such that it becomes: [ [7,4,1], [8,5,2], [9,6,3] ]
Example 2:
Given input matrix = [ [ 5, 1, 9,11], [ 2, 4, 8,10], [13, 3, 6, 7], [15,14,12,16] ], rotate the input matrix in-place such that it becomes: [ [15,13, 2, 5], [14, 3, 4, 1], [12, 6, 8, 9], [16, 7,10,11] ]
Solution: 2 Passes
First pass: mirror around diagonal
Second pass: mirror around y axis
Time complexity: O(n^2)
Space complexity: O(1)
C++
1 2 3 4 5 6 7 8 9 10 11 12 |
// Author: Huahua class Solution { public: void rotate(vector<vector<int>>& matrix) { const int n = matrix.size(); for (int i = 0; i < n; ++i) for (int j = i + 1; j < n; ++j) swap(matrix[i][j], matrix[j][i]); for (int i = 0; i < n; ++i) reverse(begin(matrix[i]), end(matrix[i])); } }; |
请尊重作者的劳动成果,转载请注明出处!花花保留对文章/视频的所有权利。
如果您喜欢这篇文章/视频,欢迎您捐赠花花。
If you like my articles / videos, donations are welcome.
Be First to Comment