Rotate Image -- LeetCode
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?
思路:将这个矩阵沿左对角线(从左上角到右下角)对称变换,再进行左右对称变换。
1 class Solution { 2 public: 3 void rotate(vector<vector<int>>& matrix) { 4 for (int i = 0, n = matrix.size(); i < n; i++) 5 for (int j = i + 1; j < n; j++) 6 swap(matrix[i][j], matrix[j][i]); 7 for (int i = 0, n = matrix.size(); i < n; i++) 8 for (int j = (n - 1) / 2 + 1; j < n; j++) 9 swap(matrix[i][j], matrix[i][n - j - 1]); 10 } 11 };