Spiral Matrix

1def spiralOrder(matrix: List[List[int]]) -> List[int]:
2    if not matrix: return []
3    res = []
4    top, bottom = 0, len(matrix) - 1
5    left, right = 0, len(matrix[0]) - 1
6    
7    while top <= bottom and left <= right:
8        # Traverse Right
9        for i in range(left, right + 1):
10            res.append(matrix[top][i])
11        top += 1
12        
13        # Traverse Down
14        for i in range(top, bottom + 1):
15            res.append(matrix[i][right])
16        right -= 1
17        
18        if top <= bottom:
19            # Traverse Left
20            for i in range(right, left - 1, -1):
21                res.append(matrix[bottom][i])
22            bottom -= 1
23            
24        if left <= right:
25            # Traverse Up
26            for i in range(bottom, top - 1, -1):
27                res.append(matrix[i][left])
28            left += 1
29            
30    return res