July 15, 2020 - 10:00 PM mock interview - interview is Microsoft SDE II, two years experience - Excellent problem solving, bug-free code

IslandPerimeter.java

import java.io.*;
import java.util.*;

/*
 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:

3
0
3
3
2
2
3

16

[[0,2,0,0],
 [2,2,2,0],
 [0,2,0,0],
 [2,2,0,0]]
 
 sum = 3
       3
       0
       3
       2
       3
       2
 
[[0,1,0,0],
 [1,1,1,0],
 [0,1,0,0],
 [1,1,0,0]]
    i
 
  i
Output: 16

http://juliachencoding.blogspot.com/2020/07/mock-interview.html
Explanation: The perimeter is the 16 yellow stripes in the image below:



 */

class Solution {
  public static void main(String[] args) {
    ArrayList<String> strings = new ArrayList<String>();
    strings.add("Hello, World!");
    strings.add("Welcome to CoderPad.");
    strings.add("This pad is running Java " + Runtime.version().feature());

    for (String string : strings) {
      System.out.println(string);
    }
  }
  
  public int islandPerimeter(int[][] grid) {
    int total = 0;
    if (grid == null || grid.length == 0 || grid[0].length) return total;
    
    for (int i = 0; i < grid.length; i++) {
      for (int j = 0; j < grid[0].length; j++) {
        if (grid[i][j] == 1) {
          int temp = 4;  // take one off - it is working 
          
          temp -= neighbor(grid, i - 1, j);
          temp -= neighbor(grid, i + 1, j);
          temp -= neighbor(grid, i, j - 1);
          temp -= neighbor(grid, i, j + 1);
          total += temp;
        }  
      }  
    }  
    return total;
  }
  
  private int neighbor(int[][] grid, int x, int y) {
    return (x < 0 || x >= grid.length || y < 0 || y >= grid[0].length || grid[x][y] == 0) ? 0 : 1;
  }  
}