Leetcode 48: Rotate Image
u 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] ]
Notes: it's a little bit tricky to come up with this solution. It can be used to solve similar problems like rotate 180/270 degree as well.
1 public class Solution { 2 public void Rotate(int[,] matrix) { 3 int rows = matrix.GetLength(0), cols = matrix.GetLength(1); 4 if (cols < 2) return; 5 6 int leftCol = 0, rightCol = cols - 1; 7 for (int i = 0; i <= rows / 2; i++) 8 { 9 for (int j = leftCol; j < rightCol; j++) 10 { 11 var tmp1 = matrix[i, j]; 12 var tmp2 = matrix[j , rows - 1 - i]; 13 var tmp3 = matrix[rows - 1 - i, rows - 1 - j]; 14 var tmp4 = matrix[rows - 1 - j, i]; 15 16 matrix[j , rows - 1 - i] = tmp1; 17 matrix[rows - 1 - i, rows - 1 - j] = tmp2; 18 matrix[rows - 1 - j, i] = tmp3; 19 matrix[i, j] = tmp4; 20 } 21 22 leftCol++; 23 rightCol--; 24 } 25 } 26 }