463-Island-Perimeter.py

class Solution:
    def islandPerimeter(self, grid: List[List[int]]) -> int:
        visit = set()
        
        def dfs(i, j):
            if i >= len(grid) or j >= len(grid[0]) or \
                i < 0 or j < 0 or grid[i][j] == 0:
                return 1
            if (i, j) in visit:
                return 0
            
            visit.add((i, j))
            perim = dfs(i, j + 1)
            perim += dfs(i + 1, j)
            perim += dfs(i, j - 1)
            perim += dfs(i - 1, j)
            return perim
        
        for i in range(len(grid)):
            for j in range(len(grid[0])):
                if grid[i][j]:
                    return dfs(i, j)