48. Rotate Image
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] ]
首先我想说,leetcode上的大神真实他妈的宇宙无敌超级他妈的几把厉害,哦也可能是我太菜
先交换行,再转置(两个可以交换顺序),就完成90度旋转了,真他妈的厉害。把我这个菜逼看的一愣一愣的
class Solution { public void rotate(int[][] matrix) { /*1. 先交换行(先转置再交换列也行,但交换列对java不友好) 2. 再转置 */ if(matrix.length<=1) return; int n = matrix.length; /* 1,2,3 4,5,6 7,8,9 */ for(int i=0;i<n/2;i++){ int[] temp = matrix[i]; matrix[i] = matrix[n-1-i]; matrix[n-1-i] = temp; } /* 7,8,9 4,5,6 1,2,3 */ for(int i=0;i<n;i++){ for(int j=i;j<n;j++){ int temp = matrix[j][i]; matrix[j][i] = matrix[i][j]; matrix[i][j] = temp; } } /* 7,4,1 8,5,2 9,6,3 */ }