From 00d8c462bfdf73d99f633cbad01cf66d9ef2cdba Mon Sep 17 00:00:00 2001
From: marina <138340846+bt3gl-cryptographer@users.noreply.github.com>
Date: Tue, 1 Aug 2023 15:21:20 -0700
Subject: [PATCH] Create matrix_bfs.py

---
 graphs/matrix_bfs.py | 48 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 graphs/matrix_bfs.py

diff --git a/graphs/matrix_bfs.py b/graphs/matrix_bfs.py
new file mode 100644
index 0000000..1c1ca0c
--- /dev/null
+++ b/graphs/matrix_bfs.py
@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# author: bt3gl
+
+'''
+You are given an m x n grid rooms initialized with these three possible values.
+
+* -1 A wall or an obstacle.
+* 0 A gate.
+* INF Infinity means an empty room (2^31 - 1 = 2147483647 to represent INF)
+
+Fill each empty room with the distance to its nearest gate. 
+If it is impossible to reach a gate, it should be filled with INF.
+'''
+
+def matrix_bfs(rooms: list[list[int]]) -> None:
+        
+        m = len(rooms)
+        if m == 0:
+           return rooms
+        n = len(rooms[0])
+        
+        GATE = 0
+        EMPTY = 2147483647
+        DIRECTIONS = ((1, 0), (-1, 0), (0, 1), (0, -1))
+
+        q = collections.deque()
+
+        for i in range(m):
+            for j in range(n):
+                
+                if rooms[i][j] == GATE:
+                    q.append((i, j))
+
+        while q:
+
+            row, col = q.popleft()
+
+            for (x, y) in DIRECTIONS:
+
+                r = row + x
+                c = col + y
+
+                if (r < 0) or (c < 0) or (r >= m) or (c >= n) or rooms[r][c] != EMPTY:
+                    continue
+
+                rooms[r][c] = rooms[row][col] + 1
+                q.append((r, c))