행렬 회전하는 법을 자꾸 까먹어서,,,,, 기록기록
def rotate_a_matrix_by_90_degree(matrix):
row = len(matrix)
column = len(matrix[0])
result=[[0] * row for _ in range(column)]
for i in range(row):
for j in range(column):
result[j][row - i - 1] = matrix[i][j]
return result