Spiral Order (From Center)

Given a positive and odd integer n, return an n x n grid filled with integers from 0 to n^2 - 1 in spiral order.

Rules:

Start at the center cell and place 0.
Move down first, then continue turning clockwise.
Keep placing the next number whenever you step into a valid cell.

Illustration (n = 5):

Spiral Order From Center (n=5)

Example:

Input: n = 3
Output: [[4,5,6],[3,0,7],[2,1,8]]


4	5	6
3	0	7
2	1	8

Explanation:
- Start at center (1,1): 0
- Move Down: (2,1) -> 1
- Move Left: (2,0) -> 2
- Move Up: (1,0) -> 3, (0,0) -> 4
- Move Right: (0,1) -> 5, (0,2) -> 6
- Move Down: (1,2) -> 7, (2,2) -> 8

1def spiralOrderCenter(n: int) -> List[List[int]]:
2    grid = [[0] * n for _ in range(n)]
3    r, c = n // 2, n // 2
4    grid[r][c] = 0
5    curr = 1
6    
7    # Directions: Down, Left, Up, Right
8    directions = [(1, 0), (0, -1), (-1, 0), (0, 1)]
9    dir_idx = 0
10    steps = 1
11    
12    while curr < n * n:
13        for _ in range(2): # Change step size every 2 directions
14            dr, dc = directions[dir_idx]
15            for _ in range(steps):
16                if curr >= n * n:
17                    break
18                r += dr
19                c += dc
20                if 0 <= r < n and 0 <= c < n:
21                    grid[r][c] = curr
22                    curr += 1
23            dir_idx = (dir_idx + 1) % 4
24        steps += 1
25        
26    return grid

Queens That Can Attack the King

Spiral Matrix

r=1

c=1

curr=1

steps=1

Step 1 / 6

Step 1:

Start at the center (1,1) with value 0.

Focus: select @ [4]

r=1c=1curr=1steps=1