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$ curl repovive.com/roadmaps/meta-interview-prep-v2/coding-patterns-ii-trees-graphs-advanced/lc-463-island-perimeter-implementation

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$ curl repovive.com/roadmaps/meta-interview-prep-v2/coding-patterns-ii-trees-graphs-advanced/lc-463-island-perimeter-implementation

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LeetCode 463 Island Perimeter - Implementation - Coding Patterns II: Trees, Graphs & Advanced | Meta Interview Prep | Repovive

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Meta Interview Prep6 sections · 147 units8h total

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LeetCode 463 Island Perimeter - Implementation

The code

For each land cell, add $4$ and subtract $1$ for each adjacent land neighbor.

Here's the solution:

function islandPerimeter(grid):
    m = rows, n = cols
    perimeter = 0
    for r in range(m):
        for c in range(n):
            if grid[r][c] == 1:
                perimeter += 4
                if r > 0 and grid[r-1][c] == 1:
                    perimeter -= 1
                if r < m-1 and grid[r+1][c] == 1:
                    perimeter -= 1
                if c > 0 and grid[r][c-1] == 1:
                    perimeter -= 1
                if c < n-1 and grid[r][c+1] == 1:
                    perimeter -= 1
    return perimeter

$O(m \times n)$ time, $O(1)$ space.