LeetCode:48. Rotate Image(旋轉圖片)
阿新 • • 發佈:2018-12-13
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-placesuch that it becomes: [ [15,13, 2, 5], [14, 3, 4, 1], [12, 6, 8, 9], [16, 7,10,11] ]
方法1:(就是一個普通的迴圈,要控制方向)
package leetcode; import org.junit.Test; /** * @author zhangyu * @version V1.0 * @ClassName: RotateImage * @Description: TOTO * @date 2018/12/13 11:29 **/ public class RotateImage { @Test public void fun() { int[][] matrix = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9} }; rotate(matrix); for (int i = 0; i < matrix.length; i++) { for (int j = 0; j < matrix[0].length; j++) { System.out.print(matrix[i][j] + " "); } System.out.println(); } } public void rotate(int[][] matrix) { if (matrix == null || matrix.length < 1) { return; } // 先進行對稱交換 for (int i = 0; i < matrix.length - 1; i++) { for (int j = i; j < matrix[0].length; j++) { swap(matrix, i, j, j, i); } } /* 1 4 7 2 5 8 3 6 9* / // 再中間進行變換 for (int i = 0; i < matrix.length; i++) { for (int j = 0; j < matrix[0].length / 2; j++) { swap(matrix, i, j, i, matrix[0].length - j - 1); } } /* 7 4 1 8 5 2 9 6 3 */ } //陣列進行交換 private void swap(int[][] nums, int x1, int y1, int x2, int y2) { int temp = nums[x1][y1]; nums[x1][y1] = nums[x2][y2]; nums[x2][y2] = temp; } }
時間複雜度:O(n^2)
空間複雜度:O(1)