You are given
row x col
grid representing a map where
grid[i][j] = 1 represents land and
grid[i][j] = 0 represents water.
Grid cells are connected horizontally/vertically (not diagonally). The
grid is completely surrounded by water, and there is exactly one island (i.e., one or more connected land cells).
The island doesn't have "lakes", meaning the water inside isn't connected to the water around the island. One cell is a square with side length 1. The grid is rectangular, width and height don't exceed 100. Determine the perimeter of the island.
Input: grid = [[0,1,0,0],[1,1,1,0],[0,1,0,0],[1,1,0,0]] Output: 16 Explanation: The perimeter is the 16 yellow stripes in the image above.
Input: grid = [] Output: 4
Input: grid = [[1,0]] Output: 4
row == grid.length
col == grid[i].length
1 <= row, col <= 100
class Solution: cnt=0 def islandPerimeter(self, grid: List[List[int]]) -> int: m, n=len(grid), len(grid) def dfs(i,j,grid): if not grid[i][j]: return grid[i][j]='#' adjacent=(i+1,j),(i-1,j),(i,j+1),(i,j-1) for ni, nj in adjacent: if ni<0 or nj<0 or ni>=m or nj>=n: self.cnt+=1 continue if grid[ni][nj]==0: self.cnt+=1 elif grid[ni][nj]==1: dfs(ni, nj, grid) for i in range(m): for j in range(n): if grid[i][j]==1: dfs(i,j,grid) return self.cnt
class Solution(object): def islandPerimeter(self, grid): """ :type grid: List[List[int]] :rtype: int """ if not grid: return 0 def sum_adjacent(i, j): adjacent = (i + 1, j), (i - 1, j), (i, j + 1), (i, j - 1) res = 0 for x, y in adjacent: if x < 0 or y < 0 or x == len(grid) or y == len(grid) or grid[x][y] == 0: res += 1 return res count = 0 for i in range(len(grid)): for j in range(len(grid)): if grid[i][j] == 1: count += sum_adjacent(i, j) return count