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artemkorsakov's solution

to Minesweeper in the Java Track

Published at Feb 13 2019 · 0 comments
Instructions
Test suite
Solution

Add the numbers to a minesweeper board.

Minesweeper is a popular game where the user has to find the mines using numeric hints that indicate how many mines are directly adjacent (horizontally, vertically, diagonally) to a square.

In this exercise you have to create some code that counts the number of mines adjacent to a square and transforms boards like this (where * indicates a mine):

+-----+
| * * |
|  *  |
|  *  |
|     |
+-----+

into this:

+-----+
|1*3*1|
|13*31|
| 2*2 |
| 111 |
+-----+

Running the tests

You can run all the tests for an exercise by entering

$ gradle test

in your terminal.

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

MinesweeperBoardTest.java

import org.junit.Ignore;
import org.junit.Test;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;

import static org.junit.Assert.assertEquals;

public class MinesweeperBoardTest {

    @Test
    public void testInputBoardWithNoRowsAndNoColumns() {
        List<String> inputBoard = Collections.emptyList();
        List<String> expectedNumberedBoard = Collections.emptyList();
        List<String> actualNumberedBoard = new MinesweeperBoard(inputBoard).withNumbers();

        assertEquals(expectedNumberedBoard, actualNumberedBoard);
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputBoardWithOneRowAndNoColumns() {
        List<String> inputBoard = Collections.singletonList("");
        List<String> expectedNumberedBoard = Collections.singletonList("");
        List<String> actualNumberedBoard = new MinesweeperBoard(inputBoard).withNumbers();

        assertEquals(expectedNumberedBoard, actualNumberedBoard);
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputBoardWithNoMines() {
        List<String> inputBoard = Arrays.asList(
                "   ",
                "   ",
                "   "
        );

        List<String> expectedNumberedBoard = Arrays.asList(
                "   ",
                "   ",
                "   "
        );

        List<String> actualNumberedBoard = new MinesweeperBoard(inputBoard).withNumbers();

        assertEquals(expectedNumberedBoard, actualNumberedBoard);
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputBoardWithOnlyMines() {
        List<String> inputBoard = Arrays.asList(
                "***",
                "***",
                "***"
        );

        List<String> expectedNumberedBoard = Arrays.asList(
                "***",
                "***",
                "***"
        );

        List<String> actualNumberedBoard = new MinesweeperBoard(inputBoard).withNumbers();

        assertEquals(expectedNumberedBoard, actualNumberedBoard);
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputBoardWithSingleMineAtCenter() {
        List<String> inputBoard = Arrays.asList(
                "   ",
                " * ",
                "   "
        );

        List<String> expectedNumberedBoard = Arrays.asList(
                "111",
                "1*1",
                "111"
        );

        List<String> actualNumberedBoard = new MinesweeperBoard(inputBoard).withNumbers();

        assertEquals(expectedNumberedBoard, actualNumberedBoard);
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputBoardWithMinesAroundPerimeter() {
        List<String> inputBoard = Arrays.asList(
                "***",
                "* *",
                "***"
        );

        List<String> expectedNumberedBoard = Arrays.asList(
                "***",
                "*8*",
                "***"
        );

        List<String> actualNumberedBoard = new MinesweeperBoard(inputBoard).withNumbers();

        assertEquals(expectedNumberedBoard, actualNumberedBoard);
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputBoardWithSingleRowAndTwoMines() {
        List<String> inputBoard = Collections.singletonList(
                " * * "
        );

        List<String> expectedNumberedBoard = Collections.singletonList(
                "1*2*1"
        );

        List<String> actualNumberedBoard = new MinesweeperBoard(inputBoard).withNumbers();

        assertEquals(expectedNumberedBoard, actualNumberedBoard);
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputBoardWithSingleRowAndTwoMinesAtEdges() {
        List<String> inputBoard = Collections.singletonList(
                "*   *"
        );

        List<String> expectedNumberedBoard = Collections.singletonList(
                "*1 1*"
        );

        List<String> actualNumberedBoard = new MinesweeperBoard(inputBoard).withNumbers();

        assertEquals(expectedNumberedBoard, actualNumberedBoard);
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputBoardWithSingleColumnAndTwoMines() {
        List<String> inputBoard = Arrays.asList(
                " ",
                "*",
                " ",
                "*",
                " "
        );

        List<String> expectedNumberedBoard = Arrays.asList(
                "1",
                "*",
                "2",
                "*",
                "1"
        );

        List<String> actualNumberedBoard = new MinesweeperBoard(inputBoard).withNumbers();

        assertEquals(expectedNumberedBoard, actualNumberedBoard);
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputBoardWithSingleColumnAndTwoMinesAtEdges() {
        List<String> inputBoard = Arrays.asList(
                "*",
                " ",
                " ",
                " ",
                "*"
        );

        List<String> expectedNumberedBoard = Arrays.asList(
                "*",
                "1",
                " ",
                "1",
                "*"
        );

        List<String> actualNumberedBoard = new MinesweeperBoard(inputBoard).withNumbers();

        assertEquals(expectedNumberedBoard, actualNumberedBoard);
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputBoardWithMinesInCross() {
        List<String> inputBoard = Arrays.asList(
                "  *  ",
                "  *  ",
                "*****",
                "  *  ",
                "  *  "
        );

        List<String> expectedNumberedBoard = Arrays.asList(
                " 2*2 ",
                "25*52",
                "*****",
                "25*52",
                " 2*2 "
        );

        List<String> actualNumberedBoard = new MinesweeperBoard(inputBoard).withNumbers();

        assertEquals(expectedNumberedBoard, actualNumberedBoard);
    }

    @Ignore("Remove to run test")
    @Test
    public void testLargeInputBoard() {
        List<String> inputBoard = Arrays.asList(
                " *  * ",
                "  *   ",
                "    * ",
                "   * *",
                " *  * ",
                "      "
        );

        List<String> expectedNumberedBoard = Arrays.asList(
                "1*22*1",
                "12*322",
                " 123*2",
                "112*4*",
                "1*22*2",
                "111111"
        );

        List<String> actualNumberedBoard = new MinesweeperBoard(inputBoard).withNumbers();

        assertEquals(expectedNumberedBoard, actualNumberedBoard);
    }

}
import java.util.List;
import java.util.stream.Collectors;

class MinesweeperBoard {
    private List<char[]> boardWithNumbers;

    MinesweeperBoard(List<String> inputBoard) {
        boardWithNumbers = getBoardWithNumbers(inputBoard);
    }

    List<String> withNumbers() {
        return boardWithNumbers.parallelStream().map(String::new).collect(Collectors.toList());
    }

    private List<char[]> getBoardWithNumbers(List<String> inputBoard) {
        List<char[]> result = inputBoard.parallelStream().map(String::toCharArray).collect(Collectors.toList());
        for (int i = 0; i < result.size(); i++) {
            for (int j = 0; j < result.get(i).length; j++) {
                if (result.get(i)[j] == '*') {
                    result = increaseSquare(result, i, j);
                }
            }
        }
        return result;
    }

    private List<char[]> increaseSquare(List<char[]> square, int row, int col) {
        if (row > 0) {
            char[] prevRow = increaseRow(square.get(row - 1), col);
            square.set(row - 1, prevRow);
        }
        char[] curRow = increaseRow(square.get(row), col);
        square.set(row, curRow);
        if (row < square.size() - 1) {
            char[] nextRow = increaseRow(square.get(row + 1), col);
            square.set(row + 1, nextRow);
        }
        return square;
    }

    private char[] increaseRow(char[] row, int col) {
        if (col > 0) {
            row[col - 1] = increaseItem(row[col - 1]);
        }
        row[col] = increaseItem(row[col]);
        if (col < row.length - 1) {
            row[col + 1] = increaseItem(row[col + 1]);
        }
        return row;
    }

    private char increaseItem(char c) {
        if (c == '*') {
            return c;
        }
        if (c == ' ') {
            return '1';
        }
        int num = Character.getNumericValue(c) + 1;
        return (char) (num + '0');
    }

}

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