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

/**
 * @param {number[][]} matrix
 * @return {void} Do not return anything, modify matrix in-place instead.
 */
var rotate = function(matrix) {
    const n = matrix.length
    for (let i = 0; i < Math.floor(n / 2); i++) {
        for (let j = i; j < n - i - 1; j++) {
            const positions = [
                [i, j],
                [j, n - 1 - i],
                [n - 1 - i, n - 1 - j],
                [n - 1 - j, i],
            ];

            let temp = matrix[positions[0][0]][positions[0][1]]
            for (let k = 1; k < positions.length; k++) {
                const [row, col] = positions[k]
                const current = matrix[row][col]
                matrix[row][col] = temp
                temp = current
            }
            matrix[positions[0][0]][positions[0][1]] = temp
        }
    }
};

export { rotate }

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