프로그래머스 - 빛의 경로 사이클 (L2)

 1dx = [1, 0, -1, 0]
 2dy = [0, 1, 0, -1]
 3def solution(grid):
 4    N = len(grid)
 5    M = len(grid[0])
 6    grid = [list(line) for line in grid]
 7    route = [[[False]*4 for _ in range(M)] for _ in range(N)]
 8    answer = []
 9    
10    for i in range(M):
11        for j in range(N):
12            for k in range(4):
13                cur = [i, j]
14                dir = k
15                cnt = 0
16                while not route[cur[1]][cur[0]][dir]:
17                    cnt += 1
18                    route[cur[1]][cur[0]][dir] = True
19                    cur[0] = (cur[0]+dx[dir]) % M
20                    cur[1] = (cur[1]+dy[dir]) % N
21
22                    if grid[cur[1]][cur[0]] == 'L':
23                        dir = (dir-1) % 4
24                    elif grid[cur[1]][cur[0]] == 'R':
25                        dir = (dir+1) % 4
26                if cnt != 0:
27                    answer.append(cnt)
28
29    return sorted(answer)