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Solution: Island Perimeter

Understand how to determine the perimeter of a single island in a rectangular grid by counting cell edges and subtracting shared boundaries. This lesson teaches how to systematically traverse a matrix, assess adjacent land cells, and compute the total outer perimeter with optimal time and space complexity.

Statement

You are given a grid with dimensions row x col, where each cell represents either land (grid[i][j] = 1) or water (grid[i][j] = 0). The grid satisfies the following conditions:

  • Cells are connected only horizontally or vertically (not diagonally).

  • The grid is surrounded by water and contains exactly one island, consisting of one or more connected land cells.

  • The island has no lakes, meaning no water is enclosed within the island that connects to the surrounding water.

  • The grid is rectangular, and each cell is a square with a side length 1.

Your task is to calculate the perimeter of the island.

Constraints:

  • row ==== grid.length

  • col == ...