#286

Walls and Gates

medium· Graphsruns: 0

You are given an m x n grid rooms initialized with one of three values: -1 for a wall, 0 for a gate, and 2147483647 (INT_MAX) for an empty room. Fill each empty room with the distance to its nearest gate. If it is impossible to reach a gate, leave the room as INT_MAX. Modify the grid in place.

wpm 0acc 100%time 0:000 / 781

from collections import deque

class Solution:
    def wallsAndGates(self, rooms: list[list[int]]) -> None:
        if not rooms:
            return
        rows, cols = len(rooms), len(rooms[0])
        queue = deque()
        for r in range(rows):
            for c in range(cols):
                if rooms[r][c] == 0:
                    queue.append((r, c))
        while queue:
            r, c = queue.popleft()
            for dr, dc in ((1, 0), (-1, 0), (0, 1), (0, -1)):
                nr, nc = r + dr, c + dc
                if (
                    0 <= nr < rows
                    and 0 <= nc < cols
                    and rooms[nr][nc] == 2147483647
                ):
                    rooms[nr][nc] = rooms[r][c] + 1
                    queue.append((nr, nc))

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