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rotateImage.go
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package rotateImage
//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]
//]
// 每次旋转4个元素
func rotate(matrix [][]int) {
l := len(matrix)
if l < 2 {
return
}
for i := 0; i < l/2; i++ {
for j := i; j < l-1-i; j++ {
// matrix(i,j) -> matrix(j,l-1-i)
matrix[i][j], matrix[l-1-j][i], matrix[l-1-i][l-1-j], matrix[j][l-1-i] =
matrix[l-1-j][i], matrix[l-1-i][l-1-j], matrix[j][l-1-i], matrix[i][j]
}
}
}