- 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:
代码语言：javascript复制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:
代码语言：javascript复制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]
]思路：
题目意思是把一个二维矩阵，顺时针旋转90度，可以一层一层的考虑，以
[[ 5, 1, 9,11],[ 2, 4, 8,10],[13, 3, 6, 7],[15,14,12,16]]为例，对于最外层，只需要把5,2,13、15,14,12、16, 7,10、11, 9, 1，顺时针移动一下就实现了这一圈的90度旋转。
代码：
go：
代码语言：javascript复制func rotate(matrix [][]int) {
if matrix == nil || len(matrix) == 0 {
return
}
var (
m = len(matrix)
top = 0
left = 0
bottom = m - 1
right = m - 1
)
for top < bottom {
for j := 0; j < right - left ; j {
temp := matrix[top][left j]
matrix[top][left j] = matrix[bottom - j][left]
matrix[bottom - j][left] = matrix[bottom][right - j]
matrix[bottom][right - j] = matrix[top j][right]
matrix[top j][right] = temp
}
top
bottom--
left
right--
}
}
