# Untitled

unknown
python
2 months ago
1.5 kB
2
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Never
```class Solution:
def closedIsland(self, grid: List[List[int]]) -> int:
# what defines an unclosed island? when a seq of 0's can reach the side of the grid
# starting from each 0 if you can complete do dfs, if we can complete dfs without having a 0 connected to the edge, that is a closed island
# within the dfs function, use a flag to keep track of if it hits the edge and only plus 1 to the result if the flag is false

maxR = len(grid) - 1
maxC = len(grid[0]) - 1

def dfs(r, c):
isClosed = 1
stack = []
stack.append((r, c))
while stack:
r, c = stack.pop()
grid[r][c] = 1
if r == 0 or r == maxR or c == 0 or c == maxC:
isClosed = False
if r - 1 >= 0 and grid[r - 1][c] == 0:
stack.append((r - 1,c))
if r + 1 <= maxR and grid[r + 1][c] == 0:
stack.append((r + 1, c))
if c - 1 >= 0 and grid[r][c - 1] == 0:
stack.append((r, c - 1))
if c + 1 <= maxC and grid[r][c + 1] == 0:
stack.append((r, c + 1))

return isClosed

res = 0
for r in range(maxR + 1):
for c in range(maxC + 1):
if grid[r][c] == 0:
if dfs(r, c):
res += 1

return res```