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