Spiral Matrix IV - Leetcode 2326 - Python

0:00 - Read the problem
0:30 - Drawing Explanation
7:45 - Coding Explanation
13:17 - Coding Explanation 2

leetcode 2326

#neetcode #leetcode #python

[NeetCodeIO]

Will also be making weekly system design videos, along with this weekly newsletter! Check it out and let me know what you think :)

[soupa]

A more clear solution in my opinion.

class Solution:
def spiralMatrix(self, m: int, n: int, head: Optional[ListNode]) -> List[List[int]]:
res = [[-1] * n for x in range(m)]

current = head
directions = [(0, 1), (1, 0), (0, -1), (-1, 0)]
d_idx = 0
i, j = 0, 0

while current:
res[i][j] = current.val
dy, dx = directions[d_idx]

# If the next move is out of bounds or if it tries to march into a pre-existing cell, change directions.
if i + dy < 0 or i + dy >= m or j + dx < 0 or j + dx >= n or res[i+dy][j+dx] > -1:
d_idx = (d_idx + 1) % len(directions)
dy, dx = directions[d_idx]

i += dy
j += dx

current = current.next

return res

[BrandonGarciaCode]

I think after solving spiral matrix I, II, III this gets more easier, because they basically have the same pattern

[akialter]

Just think it like this:
- Cells initially all -1.
- We move in this pattern (right -> down -> left -> up) * repeat.
- Set cell to current linked list node each move.
- Change direction only when you go out of bound or touch a cell not -1.
- Stop when linked list ends.

[PegasusKr]

even with 4 duplicate code blocks, i think first solution looks much much cleaner

[RajdeepJadeja]

0:15 Exactly! I was able to reach the solution just because I knew how I solved the walking robot simulation problem

[MP-nyep]

Beautifully explained! Thank you for the daily videos. Really appreciate it

[corrogist]

After watching too many NeetCode videos, this question is so intuitive to me.😅

[pratiksinha]

Oh god how many sequels will this have

[Kaviarasu_NS]

3:11 You kind of know exactly what to do, you just don’t know how to do it in terms of code, in terms of variables and loops and things like that. Well that’s what I’m gonna show you now. ❤️‍🔥❤️‍🔥