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https://leetcode.com/problems/minesweeper/

please review for performance. I really don't like the implementation I made for GetNumberOfMines() function, but within the time limits i did this. it is easy to understand but probably bad in performance.

Let's play the minesweeper game (Wikipedia, online game)!

You are given a 2D char matrix representing the game board. 'M' represents an unrevealed mine, 'E' represents an unrevealed empty square, 'B' represents a revealed blank square that has no adjacent (above, below, left, right, and all 4 diagonals) mines, digit ('1' to '8') represents how many mines are adjacent to this revealed square, and finally 'X' represents a revealed mine.

Now given the next click position (row and column indices) among all the unrevealed squares ('M' or 'E'), return the board after revealing this position according to the following rules:

If a mine ('M') is revealed, then the game is over - change it to 'X'. If an empty square ('E') with no adjacent mines is revealed, then change it to revealed blank ('B') and all of its adjacent unrevealed squares should be revealed recursively. If an empty square ('E') with at least one adjacent mine is revealed, then change it to a digit ('1' to '8') representing the number of adjacent mines. Return the board when no more squares will be revealed.

Example 1:

Input: 

[['E', 'E', 'E', 'E', 'E'],
 ['E', 'E', 'M', 'E', 'E'],
 ['E', 'E', 'E', 'E', 'E'],
 ['E', 'E', 'E', 'E', 'E']]

Click : [3,0]

Output: 

[['B', '1', 'E', '1', 'B'],
 ['B', '1', 'M', '1', 'B'],
 ['B', '1', '1', '1', 'B'],
 ['B', 'B', 'B', 'B', 'B']]

enter image description here

Note:

The range of the input matrix's height and width is [1,50]. The click position will only be an unrevealed square ('M' or 'E'), which also means the input board contains at least one clickable square. The input board won't be a stage when game is over (some mines have been revealed). For simplicity, not mentioned rules should be ignored in this problem. For example, you don't need to reveal all the unrevealed mines when the game is over, consider any cases that you will win the game or flag any squares.

using System;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace TreeQuestions
{
    [TestClass]
    public class MineSweeperTest
    {
        [TestMethod]
        public void ExampleTest()
        {
            char[][] input =
            {
             new []{'E', 'E', 'E', 'E', 'E'},
             new []{'E', 'E', 'M', 'E', 'E'},
             new []{'E', 'E', 'E', 'E', 'E'},
             new []{'E', 'E', 'E', 'E', 'E'}
            };

            char[][] output =
            {
               new []{'B', '1', 'E', '1', 'B'},
               new []{'B', '1', 'M', '1', 'B'},
               new []{'B', '1', '1', '1', 'B'},
               new []{'B', 'B', 'B', 'B', 'B'}
            };
            var mineSweeper = new MineSweeper();
            var res = mineSweeper.UpdateBoard(input, new[] { 3, 0 });
            for (var index = 0; index < res.Length; index++)
            {
                CollectionAssert.AreEqual(output[index], res[index]);
            }
        }

        [TestMethod]
        public void FailedTest()
        {
            char[][] input =
                {
                    new []{'E', 'E', 'E', 'E', 'E','E','E','E'},
                    new []{'E', 'E', 'E', 'E', 'E','E','E','M'},
                    new []{'E', 'E', 'M', 'E', 'E','E','E','E'},
                    new []{'M', 'E', 'E', 'E', 'E','E','E','E'},
                    new []{'E', 'E', 'E', 'E', 'E','E','E','E'},
                    new []{'E', 'E', 'E', 'E', 'E','E','E','E'},
                    new []{'E', 'E', 'E', 'E', 'E','E','E','E'},
                    new []{'E', 'E', 'M', 'M', 'E','E','E','E'},
                };

            char[][] output =
            {
                new []{'B', 'B', 'B', 'B', 'B','B','1','E'},
                new []{'B', '1', '1', '1', 'B','B','1','M'},
                new []{'1', '2', 'M', '1', 'B','B','1','1'},
                new []{'M', '2', '1', '1', 'B','B','B','B'},
                new []{'1', '1', 'B', 'B', 'B','B','B','B'},
                new []{'B', 'B', 'B', 'B', 'B','B','B','B'},
                new []{'B', '1', '2', '2', '1','B','B','B'},
                new []{'B', '1', 'M', 'M', '1','B','B','B'},

            };

            var mineSweeper = new MineSweeper();
            var res = mineSweeper.UpdateBoard(input, new[] { 0, 0 });
            for (var index = 0; index < res.Length; index++)
            {
                CollectionAssert.AreEqual(output[index], res[index]);
            }
        }
    }
    public class MineSweeper
    {
        public char[][] UpdateBoard(char[][] board, int[] click)
        {
            if (board == null || board.Length == 0 || board[0].Length == 0 || click == null || click.Length == 0)
            {
                return board;
            }

            int row = click[0];
            int col = click[1];

            if (board[row][col] == 'M')
            {
                board[row][col] = 'X';
                return board;
            }
            DFS(board, row, col);

            return board;
        }

        private void DFS(char[][] board, int row, int col)
        {
            if (row < 0 || col < 0 || row >= board.Length || col >= board[0].Length || board[row][col] != 'E')
            {
                return;
            }
            int numOfMines = GetNumberOfMines(board, row, col);
            if (numOfMines == 0)
            {
                //mark B and continue DFS to neighbors
                board[row][col] = 'B';
                for (int rowIn = row - 1; rowIn <= row + 1; rowIn++)
                {
                    for (int colIn = col - 1; colIn <= col + 1; colIn++)
                    {
                        if (rowIn == row && colIn == col)
                        {
                            continue;

                        }
                        DFS(board, rowIn, colIn);
                    }
                }
            }
            else
            {
                board[row][col] = numOfMines.ToString()[0];
            }
        }

        private int GetNumberOfMines(char[][] board, int row, int col)
        {
            int mines = 0;

            for (int rowIn = row - 1; rowIn <= row + 1; rowIn++)
            {
                for (int colIn = col-1; colIn <= col+1; colIn++)
                {
                    if (colIn < 0 || rowIn < 0 || rowIn >= board.Length || colIn >= board[0].Length || rowIn == row && colIn == col)
                    {
                        continue;
                    }

                    if (board[rowIn][colIn] == 'M' || board[rowIn][colIn] == 'X')
                    {
                        mines++;
                    }
                }
            }
            return mines;
        }

    }
}
\$\endgroup\$
4
  • 1
    \$\begingroup\$ if you downvote that is ok, just explain why..? \$\endgroup\$
    – Gilad
    Apr 11 '20 at 21:32
  • \$\begingroup\$ The downvote isn't mine, but I remember telling you a while back that people may not respond well to the frequency with which you post questions. It makes them look low-effort, and that attracts downvotes. As in, according to the hovertext of the downvote buton, that's exactly what the button is for. \$\endgroup\$
    – Mast
    Apr 13 '20 at 9:22
  • \$\begingroup\$ @Mast I totally disagree, I am solving programming challenges, I follow all the guidelines of the site. I am open to hear any feedback, I write unit tests for each one of challenges. these are not findMaxInArray() functions. this site is for improving code. the best and fastest way to be good at coding... is coding and getting reviews from peers such as you. however there is a person which started downvoting each question I post. a true case of A-hole in my opinion, when I have time practice coding. \$\endgroup\$
    – Gilad
    Apr 13 '20 at 10:32
  • 1
    \$\begingroup\$ I'm just saying what it looks like, don't kill the messenger. \$\endgroup\$
    – Mast
    Apr 13 '20 at 11:17

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