Assign Numbers in Minesweeper (Java)

Implement a function that assigns correct numbers in a field of Minesweeper, which is represented as a 2 dimensional array.

Example: The size of the field is 3x4, and there are bombs at the positions [0, 0] (row index = 0, column index = 0) and [0, 1] (row index = 0, column index = 1).

Then, the resulting field should be:

[[-1, -1, 1, 0],
 [2, 2, 1, 0],
 [0, 0, 0, 0]]

 

Your function should return the resulting 2D array after taking the following three arguments:

1. bombs: A list of bomb locations.  Given as an array of arrays.  Example: [[0, 0], [0, 1]] ([row index = 0, column index = 0], [row index = 0, column index = 1].  Assume that there are no duplicates.
2. num_rows: The number of rows in the resulting field.
3. num_columns: The number of columns in the resulting field.

In the resulting field:

• -1 represents that there is a bomb in that location.
• 1, 2, 3... etc. represents that there are 1, 2, 3... etc. bombs in the surrounding cells (including diagonally adjacent cells).
• 0 represents that there are no bombs in the surrounding cells.

풀이

지뢰찾기 문제라고 생각하면 편할 거 같다.

bomb에 해당하는 index에 지뢰가 있고(-1), 지뢰 근처에 있는 index들은 +1씩 더해주면 된다(상하좌우 대각선도 포함)

처음에 조건문으로 분기처리를 하다보니 너무 많아져서 고생했다...;

강사의 solution은 상하좌우 대각선을 포함해 9개의 셀을 검토하는데 

1. 여기에 조건문으로 행과 열의 범위 안에 들어오게끔 

2. 9개 셀을 돌 때 -1 아닌 곳(지뢰가 있지 않은 곳)

에 1을 더해주는 방식으로 해결함

package com.company;

public class Main {

    public static void main(String[] args) {
        // NOTE: The following input values will be used for testing your solution.
        int[][] bombs1 = {{0, 2}, {2, 0}};
//        mineSweeper(bombs1, 3, 3);
        // [[0, 1, -1],
        //  [1, 2, 1],
        //  [-1, 1, 0]]

        int[][] bombs2 = {{0, 0}, {0, 1}, {1, 2}};
        mineSweeper(bombs2, 3, 4);
        // [[-1, -1, 2, 1],
        //  [2, 3, -1, 1],
        //  [0, 1, 1, 1]]

        int[][] bombs3 = {{1, 1}, {1, 2}, {2, 2}, {4, 3}};
//        mineSweeper(bombs3, 5, 5);
        // [[1, 2, 2, 1, 0],
        //  [1, -1, -1, 2, 0],
        //  [1, 3, -1, 2, 0],
        //  [0, 1, 2, 2, 1],
        //  [0, 0, 1, -1, 1]]
    }

    // Implement your solution below.
    public static int[][] mineSweeper(int[][] bombs, int numRows, int numCols) {
        int[][] field = new int[numRows][numCols];
        for (int i = 0; i < bombs.length; i++) {
            int[] array = bombs[i];
            int rowIndex = array[0];
            int colIndex = array[1];
            field[rowIndex][colIndex] = -1;
            for (int j = rowIndex - 1; j < rowIndex + 2; j++) {
                for (int k = colIndex - 1; k < colIndex + 2; k++) {
                    if (j >= 0 && j < numRows &&
                            k >= 0 && k < numCols &&
                            field[j][k] != -1)
                        field[j][k] += 1;
                }
            }
        }
        return field;
    }
}