IslandPerimeter.java

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// You are given a map in form of a two-dimensional integer grid where 1 represents land and 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" (water inside that 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.

 

// Example:

// Input:
// [[0,1,0,0],
//  [1,1,1,0],
//  [0,1,0,0],
//  [1,1,0,0]]

// Output: 16

class Solution {
    public int islandPerimeter(int[][] grid) {
        int result = 0;
        if (grid.length == 0) { return result; }

        int rowLength = grid.length; int columnLength = grid[0].length;

        for (int row = 0; row < rowLength; row++) {
          for (int column = 0; column < columnLength; column++) {
            if (grid[row][column] == 0) { continue; }
              
            // left edge
            if (column == 0 || grid[row][column - 1] == 0) { result += 1; }
            // top edge
            if (row == 0 || grid[row - 1][column] == 0) { result += 1; }
            // right edge
            if (column == columnLength - 1 || grid[row][column + 1] == 0) { result += 1; }  
            // bottom edge
            if (row == rowLength - 1 || grid[row + 1][column] == 0) { result += 1; }
          }
        }

        return result;
    }
}