class Solution:
    def rotateMatrix(self , mat: List[List[int]], n: int) -> List[List[int]]:
        for i in range(n): # 先按照对角线交换
            for j in range(i+1, n):
                mat[i][j], mat[j][i] = mat[j][i], mat[i][j]
        
        for row in mat: 
            row.reverse()
        
        return mat