Instructions

Test suite

Solution

Count the rectangles in an ASCII diagram like the one below.

   +--+
  ++  |
+-++--+
|  |  |
+--+--+

The above diagram contains 6 rectangles:



+-----+
|     |
+-----+

   +--+
   |  |
   |  |
   |  |
   +--+

   +--+
   |  |
   +--+



   +--+
   |  |
   +--+



+--+
|  |
+--+


  ++
  ++

You may assume that the input is always a proper rectangle (i.e. the length of every line equals the length of the first line).

Setup

Go through the setup instructions for Java to install the necessary dependencies:

https://exercism.io/tracks/java/installation

Running the tests

You can run all the tests for an exercise by entering the following in your terminal:

$ gradle test

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by removing the @Ignore("Remove to run test") annotation.

Submitting Incomplete Solutions

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

RectangleCounterTest.java

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

import static org.junit.Assert.assertEquals;

public class RectangleCounterTest {

    private RectangleCounter rectangleCounter;

    @Before
    public void setUp() {
        rectangleCounter = new RectangleCounter();
    }

    @Test
    public void testInputWithNoRowsContainsNoRectangles() {
        String[] inputGrid = new String[]{};

        assertEquals(0, rectangleCounter.countRectangles(inputGrid));
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputWithNoColumnsContainsNoRectangles() {
        String[] inputGrid = new String[]{""};

        assertEquals(0, rectangleCounter.countRectangles(inputGrid));
    }

    @Ignore("Remove to run test")
    @Test
    public void testNonTrivialInputWithNoRectangles() {
        String[] inputGrid = new String[]{" "};

        assertEquals(0, rectangleCounter.countRectangles(inputGrid));
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputWithOneRectangle() {
        String[] inputGrid = new String[]{
            "+-+",
            "| |",
            "+-+"
        };

        assertEquals(1, rectangleCounter.countRectangles(inputGrid));
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputWithTwoRectanglesWithoutSharedEdges() {
        String[] inputGrid = new String[]{
            "  +-+",
            "  | |",
            "+-+-+",
            "| |  ",
            "+-+  "
        };

        assertEquals(2, rectangleCounter.countRectangles(inputGrid));
    }

    @Ignore("Remove to run test")
    @Test
    public void testInputWithFiveRectanglesWithSharedEdges() {
        String[] inputGrid = new String[]{
            "  +-+",
            "  | |",
            "+-+-+",
            "| | |",
            "+-+-+"
        };

        assertEquals(5, rectangleCounter.countRectangles(inputGrid));
    }

    @Ignore("Remove to run test")
    @Test
    public void testThatRectangleOfHeightOneIsCounted() {
        String[] inputGrid = new String[]{
            "+--+",
            "+--+"
        };

        assertEquals(1, rectangleCounter.countRectangles(inputGrid));
    }

    @Ignore("Remove to run test")
    @Test
    public void testThatRectangleOfWidthOneIsCounted() {
        String[] inputGrid = new String[]{
            "++",
            "||",
            "++"
        };

        assertEquals(1, rectangleCounter.countRectangles(inputGrid));
    }

    @Ignore("Remove to run test")
    @Test
    public void testThatOneByOneSquareIsCounted() {
        String[] inputGrid = new String[]{
            "++",
            "++"
        };

        assertEquals(1, rectangleCounter.countRectangles(inputGrid));
    }

    @Ignore("Remove to run test")
    @Test
    public void testThatIncompleteRectanglesAreNotCounted() {
        String[] inputGrid = new String[]{
            "  +-+",
            "    |",
            "+-+-+",
            "| | -",
            "+-+-+"
        };

        assertEquals(1, rectangleCounter.countRectangles(inputGrid));
    }

    @Ignore("Remove to run test")
    @Test
    public void testThatRectanglesOfDifferentSizesAreAllCounted() {
        String[] inputGrid = new String[]{
            "+------+----+",
            "|      |    |",
            "+---+--+    |",
            "|   |       |",
            "+---+-------+"
        };

        assertEquals(3, rectangleCounter.countRectangles(inputGrid));
    }

    @Ignore("Remove to run test")
    @Test
    public void testThatIntersectionsWithoutCornerCharacterDoNotCountAsRectangleCorners() {
        String[] inputGrid = new String[]{
            "+------+----+",
            "|      |    |",
            "+------+    |",
            "|   |       |",
            "+---+-------+"
        };

        assertEquals(2, rectangleCounter.countRectangles(inputGrid));
    }

    @Ignore("Remove to run test")
    @Test
    public void testLargeInputWithManyRectangles() {
        String[] inputGrid = new String[]{
            "+---+--+----+",
            "|   +--+----+",
            "+---+--+    |",
            "|   +--+----+",
            "+---+--+--+-+",
            "+---+--+--+-+",
            "+------+  | |",
            "          +-+"
        };

        assertEquals(60, rectangleCounter.countRectangles(inputGrid));
    }

}

src/main/java/RectangleCounter.java

import java.util.stream.IntStream;

public class RectangleCounter
{

	public RectangleCounter(){}

	public int countRectangles(String[] inputGrid)
	{
		if ((inputGrid.length == 0) || ("".equals(inputGrid[0].trim()))){
			return 0;
		}

		return IntStream.range(0, inputGrid.length).map(i -> this.searchVertexOnY(inputGrid, i)).sum();
	}

	private int searchVertexOnY(String[] inputGrid, final int i)
	{
		return IntStream.range(0, inputGrid[i].length()).map(j -> this.searchVertexOnX(inputGrid, j, i)).sum();
	}

	private int searchVertexOnX(String[] inputGrid, final int j, final int i)
	{
		int count = 0;
		if (inputGrid[i].charAt(j) == '+'){
			// Search vertex on X
			int jMax = IntStream.range(j+1, inputGrid[i].length()).filter(x -> ((inputGrid[i].charAt(x) != '+') && (inputGrid[i].charAt(x) != '-')))
																  .findFirst()
																  .orElse(inputGrid[i].length());
			count += IntStream.range(j+1, jMax).map(x -> this.searchVertexOnX(inputGrid, j, i, x)).sum();
		}
		return count;
	}

	private int searchVertexOnX(String[] inputGrid, final int j, final int i, final int x)
	{
		int count = 0;
		if (inputGrid[i].charAt(x) == '+'){
			// Search vertex on Y
			int iMax = IntStream.range(i+1, inputGrid.length).filter(y -> (inputGrid[y].charAt(j) != '+') && (inputGrid[y].charAt(j) != '|'))
															 .findFirst()
															 .orElse(inputGrid.length);
			count += IntStream.range(i+1, iMax).filter(y -> this.searchVertexOnY(inputGrid, j, i, x, y)).count();
		}
		return count;
	}

	private boolean searchVertexOnY(String[] inputGrid, final int j, final int i, final int x, final int y)
	{
		boolean foundVertexOnY = false;
		if (inputGrid[y].charAt(j) == '+'){
			// Search last vertex (X, Y)
			if (inputGrid[y].charAt(x) == '+'){
				// Validate rectangle
				if (this.validateRectangle(inputGrid, j, i, x, y)){
					foundVertexOnY = true;
				}
			}
		}
		return foundVertexOnY;
	}

	private boolean validateRectangle(String[] inputGrid, final int j, final int i, final int x, final int y)
	{
		boolean validRectangle = IntStream.range(i+1, y).allMatch(y0 -> ((inputGrid[y0].charAt(x) == '|') || (inputGrid[y0].charAt(x) == '+')));
		if (validRectangle){
			validRectangle = IntStream.range(j+1, x).allMatch(x0 -> (inputGrid[y].charAt(x0) == '-') || (inputGrid[y].charAt(x0) == '+'));
		}
		return validRectangle;
	}

}

src/test/java/RectangleCounterTest.java

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

import static org.junit.Assert.assertEquals;

public class RectangleCounterTest {

    private RectangleCounter rectangleCounter;

    @Before
    public void setUp() {
        rectangleCounter = new RectangleCounter();
    }

    @Test
    public void testInputWithNoRowsContainsNoRectangles() {
        String[] inputGrid = new String[]{};

        assertEquals(0, rectangleCounter.countRectangles(inputGrid));
    }

    //@Ignore("Remove to run test")
    @Test
    public void testInputWithNoColumnsContainsNoRectangles() {
        String[] inputGrid = new String[]{""};

        assertEquals(0, rectangleCounter.countRectangles(inputGrid));
    }

    //@Ignore("Remove to run test")
    @Test
    public void testNonTrivialInputWithNoRectangles() {
        String[] inputGrid = new String[]{" "};

        assertEquals(0, rectangleCounter.countRectangles(inputGrid));
    }

    //@Ignore("Remove to run test")
    @Test
    public void testInputWithOneRectangle() {
        String[] inputGrid = new String[]{
            "+-+",
            "| |",
            "+-+"
        };

        assertEquals(1, rectangleCounter.countRectangles(inputGrid));
    }

    //@Ignore("Remove to run test")
    @Test
    public void testInputWithTwoRectanglesWithoutSharedEdges() {
        String[] inputGrid = new String[]{
            "  +-+",
            "  | |",
            "+-+-+",
            "| |  ",
            "+-+  "
        };

        assertEquals(2, rectangleCounter.countRectangles(inputGrid));
    }

    //@Ignore("Remove to run test")
    @Test
    public void testInputWithFiveRectanglesWithSharedEdges() {
        String[] inputGrid = new String[]{
            "  +-+",
            "  | |",
            "+-+-+",
            "| | |",
            "+-+-+"
        };

        assertEquals(5, rectangleCounter.countRectangles(inputGrid));
    }

    //@Ignore("Remove to run test")
    @Test
    public void testThatRectangleOfHeightOneIsCounted() {
        String[] inputGrid = new String[]{
            "+--+",
            "+--+"
        };

        assertEquals(1, rectangleCounter.countRectangles(inputGrid));
    }

    //@Ignore("Remove to run test")
    @Test
    public void testThatRectangleOfWidthOneIsCounted() {
        String[] inputGrid = new String[]{
            "++",
            "||",
            "++"
        };

        assertEquals(1, rectangleCounter.countRectangles(inputGrid));
    }

    //@Ignore("Remove to run test")
    @Test
    public void testThatOneByOneSquareIsCounted() {
        String[] inputGrid = new String[]{
            "++",
            "++"
        };

        assertEquals(1, rectangleCounter.countRectangles(inputGrid));
    }

    //@Ignore("Remove to run test")
    @Test
    public void testThatIncompleteRectanglesAreNotCounted() {
        String[] inputGrid = new String[]{
            "  +-+",
            "    |",
            "+-+-+",
            "| | -",
            "+-+-+"
        };

        assertEquals(1, rectangleCounter.countRectangles(inputGrid));
    }

    //@Ignore("Remove to run test")
    @Test
    public void testThatRectanglesOfDifferentSizesAreAllCounted() {
        String[] inputGrid = new String[]{
            "+------+----+",
            "|      |    |",
            "+---+--+    |",
            "|   |       |",
            "+---+-------+"
        };

        assertEquals(3, rectangleCounter.countRectangles(inputGrid));
    }

    //@Ignore("Remove to run test")
    @Test
    public void testThatIntersectionsWithoutCornerCharacterDoNotCountAsRectangleCorners() {
        String[] inputGrid = new String[]{
            "+------+----+",
            "|      |    |",
            "+------+    |",
            "|   |       |",
            "+---+-------+"
        };

        assertEquals(2, rectangleCounter.countRectangles(inputGrid));
    }

    //@Ignore("Remove to run test")
    @Test
    public void testLargeInputWithManyRectangles() {
        String[] inputGrid = new String[]{
            "+---+--+----+",
            "|   +--+----+",
            "+---+--+    |",
            "|   +--+----+",
            "+---+--+--+-+",
            "+---+--+--+-+",
            "+------+  | |",
            "          +-+"
        };

        assertEquals(60, rectangleCounter.countRectangles(inputGrid));
    }

}

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JuanMa's solution

to Rectangles in the Java Track