解題 22. Rotate Image

14 1 月, 2022 欣迪

出處： https://leetcode.com/explore/interview/card/top-interview-questions-easy/92/array/770/

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

var rotate = function(matrix) {
    for(let i = 0; i < matrix.length; i++) {
        for(let j = i; j < matrix.length; j++ ) {
            let temp = matrix[i][j]
            matrix[i][j] = matrix[j][i]
            matrix[j][i] = temp
        }
    }
    for(let i = 0; i < matrix.length; i++) {
        for(let j = 0; j < Math.floor(matrix.length / 2); j++ ) {
            let temp = matrix[i][j]
            matrix[i][j] = matrix[i][matrix.length - j - 1]
            matrix[i][matrix.length - j - 1] = temp
        }
    }
};

這題一樣麻煩的是不能複製陣列，必須直接修改元的的陣列內容。

兩個步驟處理會比較單純。以一個 9 x 9 的矩陣為例