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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]]

Example 3:

Input: matrix = [[1]]

Output: [[1]]

Example 4:

Input: matrix = [[1,2],[3,4]]

Output: [[3,1],[4,2]]

Constraints:

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

Solution

/*
 Do not return anything, modify matrix in-place instead.
 */
function rotate(matrix: number[][]): void {
    let len = matrix.length
    for (let i = 0; i < len; i++) {
        const tempArr = []
        for (let j = len - 1; j >= 0; j--) {
            tempArr.push(matrix[j][i])
        }
        matrix.push(tempArr)
    }
    while (len > 0) {
        matrix.shift()
        len--
    }
}

export { rotate }

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