LeetCode-in-All

48. Rotate Image

Medium

You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

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:

Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]

Output: [[7,4,1],[8,5,2],[9,6,3]]

Example 2:

Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]

Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]

Constraints:

• n == matrix.length == matrix[i].length
• 1 <= n <= 20
• -1000 <= matrix[i][j] <= 1000

Solution

func rotate(matrix [][]int) {
	n := len(matrix)
	for i := 0; i < n/2; i++ {
		for j := i; j < n-i-1; j++ {
			pos := [][]int{
				{i, j}, {j, n - 1 - i}, {n - 1 - i, n - 1 - j}, {n - 1 - j, i},
			}
			t := matrix[pos[0][0]][pos[0][1]]
			for k := 1; k < len(pos); k++ {
				temp := matrix[pos[k][0]][pos[k][1]]
				matrix[pos[k][0]][pos[k][1]] = t
				t = temp
			}
			matrix[pos[0][0]][pos[0][1]] = t
		}
	}
}

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