RotateImage.go

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]
//]
//
//Accepted.

func rotate(matrix [][]int) {
	matrixLength := len(matrix)
	// Reverse
	for i := 0; i < matrixLength/2; i++ {
		j := matrixLength - 1 - i
		cache := matrix[i]
		matrix[i] = matrix[j]
		matrix[j] = cache
	}
	// Transpose
	for i := 0; i < matrixLength; i++ {
		for j := i + 1; j < matrixLength; j++ {
			cache := matrix[i][j]
			matrix[i][j] = matrix[j][i]
			matrix[j][i] = cache
		}
	}
}