leetcode 每日一题 48. 旋转图像

Posted 2020-12-23 nil_f

转置加翻转

思路:

先把矩阵转置，然后把每一行元素翻转。即遍历元素，交换matrix[i][j]和matrix[j][i]，然后翻转每一个子数组。

代码：

 

class Solution:
    def rotate(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """
        n = len(matrix)
        for i in range(n):
            for j in range(i,n):
                matrix[j][i],matrix[i][j] = matrix[i][j],matrix[j][i]
        for i in range(n):
            matrix[i].reverse()

遍历旋转

思路:

遍历交换4条边上的元素。

代码:

class Solution:
    def rotate(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: void Do not return anything, modify matrix in-place instead.
        """
        n = len(matrix[0])        
        for i in range(n // 2 + n % 2):
            for j in range(n // 2):
                tmp = matrix[n - 1 - j][i]
                matrix[n - 1 - j][i] = matrix[n - 1 - i][n - j - 1]
                matrix[n - 1 - i][n - j - 1] = matrix[j][n - 1 -i]
                matrix[j][n - 1 - i] = matrix[i][j]
                matrix[i][j] = tmp