Safe zone (with.Java)

This article looks into the “safe zone (with.Java)” issue.

As I solve coding test problems, I look back on the problems I solved and look into different solution methods to learn more.

Let’s look at the problem first.

problem

The area with the mine and the diagonal spaces above, below, left, and right adjacent to the mine are all classified as dangerous areas.

Mines are marked as 1 on a two-dimensional array board, and on the board there are only area 1 with mines buried and area 0 without mines.

When the map board of a landmine-laden area is given as a parameter, complete the solution function to return the number of safe area squares.

Restrictions

• board is an n x n array.
• 1 ≤ n ≤ 100
• Mines are marked with 1. -On the board, there is only area 1 with mines and area 0 without mines.

Input/Output Example

My solution to the problem

class Solution {
 public int solution(int[][] board) {
 int[][] secondArr = new int[board.length+2][board.length+2];
 int answer = 0;
 for(int i = 0; i < board.length; i++){
 for(int j = 0; j < board.length; j++){
 if(board[i][j] == 1){
 for(int a = i; a <= i+2; a++){
 for(int b = j; b <= j+2; b++){
 if(secondArr[a][b] != 1){
 secondArr[a][b] = 1;
 }
 }
 }
 }
 }
 }
 for(int i = 1; i < secondArr.length - 1; i++){
 for(int j = 1; j < secondArr.length-1; j++){
 if(secondArr[i][j] == 0){
 answer++;
 }
 }
 }
 return answer;
 }
}

Solution explanation

• Create a new 2-dimensional array: Create a new 2-dimensional array, secondArr, whose size is 1 larger than the existing board array. This is to handle the border portion of the board.
• Board search and surrounding cell update: When searching the existing board and finding a cell with a value of 1, all 8 surrounding cells around that cell are updated to 2.
• Searching a new array and counting the number of cells with a value of 0: Searching a new array, counting the number of cells with a value of 0 and storing them in the answer variable.
• Return result: Returns the number of cells that are finally counted as 0.

Code pros and cons

• Advantage: The code is concise by using an efficient method of counting zero cells. The border areas of the board can be easily handled without any additional processing.
• Disadvantage: This code processes all cells on the board by traversing them one more time, which can result in inefficient execution time. Performance may be affected, especially if the board is large.