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83 lines
2.2 KiB
Python
83 lines
2.2 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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Given an m x n 2D binary grid grid which represents a map of
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'1's (land) and '0's (water), return the number of islands.
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An island is surrounded by water and is formed by connecting
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adjacent lands horizontally or vertically. You may assume all
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four edges of the grid are all surrounded by water.
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'''
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def num_island_dfs(grid) -> int:
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LAND = '1'
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answer = 0
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#######################
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### go dfs
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#######################
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def dfs(row, col):
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if row < 0 or row >= len(grid) or col < 0 or col >= len(grid[0]) or grid[row][col] != LAND:
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return
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grid[row][col] = 'x'
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dfs(row + 1, col)
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dfs(row - 1, col)
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dfs(row, col - 1)
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dfs(row, col + 1)
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#######################
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## loop through the board
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#######################
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for i in range(len(grid)):
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for j in range(len(grid[0])):
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if grid[i][j] == LAND:
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answer += 1
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dfs(i, j)
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return answer
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def num_island_bfs(grid) -> int:
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LAND = '1'
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answer = 0
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queue = collections.deque()
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#######################
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### go dfs
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#######################
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def bfs(row, col, queue):
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delta = [(1, 0), (0, 1), (-1, 0), (0, -1)]
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while queue:
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x, y = queue.popleft()
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for dx, dy in delta:
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px, py = x + dx, y + dy
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if px < 0 or px >= len(grid) or py < 0 or py >= len(grid[0]) or grid[px][py] != LAND:
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continue
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grid[px][py] = 'x'
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queue.append((px, py))
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#######################
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## loop through the board
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#######################
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for i in range(len(grid)):
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for j in range(len(grid[0])):
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if grid[i][j] == LAND:
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answer += 1
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queue.append((i, j))
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bfs(i, j, queue)
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return answer
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