433. Number of Islands
Description:
Given a boolean 2D matrix, 0 is represented as the sea, 1 is represented as the island. If two 1 is adjacent, we consider them in the same island. We only consider up/down/left/right adjacent.
Find the number of islands.
Example
Given graph:
[
[1, 1, 0, 0, 0],
[0, 1, 0, 0, 1],
[0, 0, 0, 1, 1],
[0, 0, 0, 0, 0],
[0, 0, 0, 0, 1]
]
return 3.
Code:
class Solution:
"""
@param grid: a boolean 2D matrix
@return: an integer
"""
def numIslands(self, grid):
# Write your code here
m = len(grid)
if m==0:
return 0
n = len(grid[0])
if n==0:
return 0
count = 0
for i in range(m):
for j in range(n):
if grid[i][j]==True:
self.islandErase(grid,i,j)
count +=1
return count
def islandErase(self,grid,i,j):
if i<0 or j<0 or i>=len(grid) or j>=len(grid[0]):
return
if grid[i][j]==True:
grid[i][j]=False
self.islandErase(grid,i-1,j)
self.islandErase(grid,i+1,j)
self.islandErase(grid,i,j-1)
self.islandErase(grid,i,j+1)