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number-of-islands.py
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number-of-islands.py
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"""
Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands.
An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.
Example 1:
Input: grid = [
["1","1","1","1","0"],
["1","1","0","1","0"],
["1","1","0","0","0"],
["0","0","0","0","0"]
]
Output: 1
Example 2:
Input: grid = [
["1","1","0","0","0"],
["1","1","0","0","0"],
["0","0","1","0","0"],
["0","0","0","1","1"]
]
Output: 3
Constraints:
m == grid.length
n == grid[i].length
1 <= m, n <= 300
grid[i][j] is '0' or '1'.
"""
from typing import List
class Solution:
def numIslands(self, grid: List[List[str]]) -> int:
num_islands = 0
rows = len(grid)
cols = len(grid[0])
def traverseIsland(row:int, col:int):
# Need return condition
if row < 0 or col < 0 or row >= rows or col >= cols:
return
if grid[row][col] == "0":
return
grid[row][col] = "0"
traverseIsland(row - 1, col)
traverseIsland(row + 1, col)
traverseIsland(row, col - 1)
traverseIsland(row, col + 1)
for i in range(rows):
for j in range(cols):
if grid[i][j] == "1":
traverseIsland(i, j)
num_islands += 1
return num_islands