54. Spiral Matrix

main.py

class Solution:
    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
        
        i, j = 0, 0
        left, right, down, up = False, True, False, False
        n, m = len(matrix), len(matrix[0])
        res = []
        visited = set()
        
        def is_wall(i, j):
            if i >= n or i < 0 or j >= m or j <0:
                return True
            if (i, j) in visited:
                return True
            return False
        
        for _ in range(n*m):
            if right:
                if not is_wall(i, j):
                    res.append(matrix[i][j])
                    visited.add((i, j))
                if is_wall(i, j+1):
                    right = False
                    down = True if is_wall(i-1, j) else False
                    up = not down
                    i = i + 1 if down else i - 1
                else:
                    j += 1
            if left:
                if not is_wall(i, j):
                    res.append(matrix[i][j])
                    visited.add((i, j))
                if is_wall(i, j-1):
                    left = False
                    down = True if is_wall(i-1, j) else False
                    up = not down
                    i = i + 1 if down else i - 1
                else:
                    j -= 1
            if up:
                if not is_wall(i, j):
                    res.append(matrix[i][j])
                    visited.add((i, j))
                if is_wall(i-1, j):
                    up = False
                    right = True if is_wall(i, j-1) else False
                    left = not right
                    j = j + 1 if right else j - 1
                else:
                    i -= 1
            if down:
                if not is_wall(i, j):
                    res.append(matrix[i][j])
                    visited.add((i, j))
                if is_wall(i+1, j):
                    down = False
                    right = True if is_wall(i, j-1) else False
                    left = not right
                    j = j + 1 if right else j - 1
                else:
                    i += 1
        return res