48.go

package easy_collection

/**
 * 48. Rotate Image
 * <p>
 * You are given an n x n 2D matrix representing an image.
 * <p>
 * Rotate the image by 90 degrees (clockwise).
 * <p>
 * Note:
 * <p>
 * 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.
 * <p>
 * Example 1:
 * <p>
 * Given input matrix =
 * <p>
 * [
 * [1,2,3],
 * [4,5,6],
 * [7,8,9]
 * ],
 * <p>
 * rotate the input matrix in-place such that it becomes:
 * <p>
 * [
 * [7,4,1],
 * [8,5,2],
 * [9,6,3]
 * ]
 * <p>
 * Example 2:
 * <p>
 * Given input matrix =
 * <p>
 * [
 * [ 5, 1, 9,11],
 * [ 2, 4, 8,10],
 * [13, 3, 6, 7],
 * [15,14,12,16]
 * ],
 * <p>
 * rotate the input matrix in-place such that it becomes:
 * <p>
 * [
 * [15,13, 2, 5],
 * [14, 3, 4, 1],
 * [12, 6, 8, 9],
 * [16, 7,10,11]
 * ]
 */

func rotate(matrix [][]int) {
	left := 0
	right := len(matrix) - 1
	for left < right {
		temp := matrix[left]
		matrix[left] = matrix[right]
		matrix[right] = temp
		left++
		right--
	}
	for i := 0; i < len(matrix); i++ {
		for j := i + 1; j < len(matrix[i]); j++ {
			temp := matrix[i][j]
			matrix[i][j] = matrix[j][i]
			matrix[j][i] = temp
		}
	}
}