You are given row x colgrid 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.
class Solution: # Time: O(row * col) every cell inspected once # Space: O(1) def island_perimeter(self, grid: list[list[int]]) -> int: rows = len(grid) cols = len(grid[0]) perimeter = 0 for r in range(rows): for c in range(cols): if grid[r][c] == 0: continue # Each land cell starts with 4 exposed sides; subtract shared edges. exposed = 4 for dr, dc in ((-1, 0), (1, 0), (0, -1), (0, 1)): nr, nc = r + dr, c + dc if 0 <= nr < rows and 0 <= nc < cols and grid[nr][nc] == 1: exposed -= 1 perimeter += exposed return perimeter
