How to draw an ASCII staircase with Java?

Question

I've been trying to get this done in Java. And this is a complex thing to draw, at least for me.

Q1 Write a simple Java program that prints a staircase or a figure as shown below:

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

I have come up with a solution but it is not even halfway there. This is the code I have come up with

public class DrawStairs {
    public static final int HEIGHT = 5;
    public static final int TOTALHEIGHT = HEIGHT * 5;
    public static void main(String[] args) {
        //Main Outer Loop
        for (int i = 1; i <= HEIGHT; i++) {
            //Loop for the spaces before, then print the head
            for (int j = 1; j <= TOTALHEIGHT + (i * (-5)); j++) {
                System.out.print(" ");
            }
            printTop();
            //Loop for spaces after, then print asterisk
            for (int j = 1; j <= (i - 1); j++) {
                System.out.print("---+");
            }
            System.out.println(" ");
            //Loop for the spaces before, then print the body
            for (int j = 1; j <= TOTALHEIGHT + (i * (-5)); j++) {
                System.out.print(" ");
            }
            printMiddle();
            //Loop for spaces after, then print asterisk
            for (int j = 1; j <= (i - 1) * 5; j++) {
                System.out.print(" ");
            }
            //Loop for spaces before, then print the legs
            for (int j = 1; j <= TOTALHEIGHT + (i * (-5)); j++) {
                System.out.print(" ");
            }
            printBottom();
            //Loop for spaces after, then print asterisk
            for (int j = HEIGHT; j <= 0; --j) {
                System.out.print("---+");
            }
            System.out.println("|");
        }
        // for loop for printing the floor of asterisks
        for (int i = 1; i <= HEIGHT; i++) {
            System.out.print("+---+");
        }
    }
    public static void printTop() {
        System.out.print("+---+");
    }
    public static void printMiddle() {
        System.out.print("|   |");
    }
    public static void printBottom() {
        // System.out.print("+---+");
    }
}

And this is what it does.

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

Can anyone please help me and guide me with my code? I'd like if someone can tell me what's wrong and what should be changed.

Answer 1

This is my solution to the problem. Thanks for the puzzle;)

public class Staircase {
    public static final int SIZE = 5;
    public static final int STAIR_WIDTH = 5;
    public static final String TREAD = "-";
    public static final String RISER = "|";
    public static final String NOSING = "+";
    public static final String HOLLOW = " ";

    public static void main(String[] args)
    {
        StringBuilder step = new StringBuilder();
        for (int i = 0; i < (STAIR_WIDTH - 2); ++i) { step.append(TREAD); }
        StringBuilder hollow = new StringBuilder();
        for (int i = 0; i < (STAIR_WIDTH - 2); ++i) { hollow.append(HOLLOW); }

        StringBuilder tread = new StringBuilder();
        for (int i = 0; i < SIZE; ++i) { tread.append(NOSING + step); }
        tread.append(NOSING);

        StringBuilder riser = new StringBuilder();
        for (int i = 0; i < SIZE; ++i) { riser.append(RISER + hollow); }
        riser.append(RISER);

        for (int i = 0; i < SIZE; ++i) {
            int offset = tread.length() - (((STAIR_WIDTH - 1) * i) + STAIR_WIDTH);
            printSpaces(offset);
            System.out.println(tread.substring(offset));
            printSpaces(offset);
            System.out.println(riser.substring(offset));
        }
        System.out.println(tread);
    }

    public static void printSpaces(int count)
    {
        for (int i = 0; i < count; ++i)
            System.out.print(" ");
    }
}

Answer 2

public class Staircase {
    // You can change the height to any number and check
    public static final int HEIGHT = 5;

    public static void main(String[] args) {
        Staircase stairs = new Staircase();
        for (int j = 0; j < HEIGHT; j++) {
            stairs.printSpace(j);
            stairs.printTop(j);
            stairs.printSpace(j);
            stairs.printMiddle(j);
        }
       stairs.printTop(HEIGHT-1); // added for bottom line stairs 
    }

    public void printSpace(int j) {
        for (int i = j; i < HEIGHT - 1; i++) {
            System.out.print("   ");
        }
    }

    public void printTop(int j) {

        for (int k = 0; k <= j; k++) {
            System.out.print("+--");
        }

        System.out.print("+");
        System.out.println("");
    }

    public void printMiddle(int j) {
        for (int k = 0; k <= j; k++) {
            System.out.print("|  ");
        }
        System.out.print("|");
        System.out.println("");
    }
}

Answer 3

Yet another answer, so you can see the many, many ways that this problem can be solved. This one uses a single paint loop, and avoids use of constants:

public static void drawStaircase(int steps, 
      String stepTop, String stepLeft, String stepEmpty) {
    String endOfTopStep = stepTop.substring(0,1);  // "+---" => "+"
    String endOfMidStep = stepLeft.substring(0,1); // "|---" => "|"
    for (int row=0; row<steps;row++) {
        // paint a top-of-step row
        for (int col=0; col<steps; col++) {
            boolean isEmpty = row+col+1 < steps;
            System.out.print(isEmpty ? stepEmpty : stepTop);
        }
        System.out.println(endOfTopStep);
        
        // paint a middle-of-step row
        for (int col=0; col<steps; col++) {
            boolean isEmpty = row+col+1 < steps;
            System.out.print(isEmpty ? stepEmpty : stepLeft);
        }
        System.out.println(endOfMidStep);
    }
    // paint bottom border
    for (int col=0; col<steps; col++) {
        System.out.print(stepTop);
    }
    System.out.println(endOfTopStep);
}

public static void main(String ...args) {
    drawStaircase(4, "+---", "|   ", "    ");
}

Answer 4

I created this code to illustrate how to take a problem and break it down step by step until you can solve each step.

Here are the results from one of my many test results.

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

The first thing I did was create a method to produce a blank segment. I used the StringBuilder class to make it easier to build line segments and concatenate them.

Once I got that working, I created methods to create a step (landing) and a joist.

Next, I created a method to create one line of the output.

Finally, I created a method to create the entire staircase.

Here's the complete runnable code. It may not be the most efficient code, but I hope that it's among the most understandable code.

public class Staircase {

    public static void main(String[] args) {
        Staircase sc = new Staircase();
        System.out.println(sc.createStaircase(5));
    }

    public String createStaircase(int steps) {
        StringBuilder builder = new StringBuilder();
        int blankSteps = 0;
        String step = createStepSegment();
        String joist = createJoistSegment();

        for (int i = 1; i <= steps; i++) {
            blankSteps = Math.max(0, steps - i);
            builder.append(createLine(step, steps, blankSteps));
            builder.append(createLine(joist, steps, blankSteps));
        }
        builder.append(createLine(step, steps, blankSteps));

        return builder.toString();
    }

    private StringBuilder createLine(String string, int steps, int blankSteps) {
        StringBuilder builder = new StringBuilder();

        int width = string.length() * blankSteps;
        builder.append(createBlankSegment(width));

        int boxSteps = steps - blankSteps;
        for (int i = 0; i < boxSteps; i++) {
            builder.append(string);
        }

        builder.append(string.charAt(0));
        builder.append(System.lineSeparator());

        return builder;
    }

    private String createStepSegment() {
        return "+---";
    }

    private String createJoistSegment() {
        return "|   ";
    }

    private StringBuilder createBlankSegment(int length) {
        StringBuilder builder = new StringBuilder();

        for (int i = 0; i < length; i++) {
            builder.append(" ");
        }

        return builder;
    }

}

Answer 5

You can use streams to build a staircase:

int m = 5;
String[] arr = IntStream.range(0, m).mapToObj(i -> {
    String[] arr1 = new String[m];
    String[] arr2 = new String[m];
    String[] arr3 = new String[m];
    IntStream.range(0, m).forEach(j -> {
        if (i + j >= m - 1) {
            if (j == m - 1) {
                arr1[j] = "+---+";
                arr2[j] = "|   |";
                arr3[j] = "+---+";
            } else {
                arr1[j] = "+---";
                arr2[j] = "|   ";
                arr3[j] = "+---";
            }
        } else {
            arr1[j] = "    ";
            arr2[j] = "    ";
        }
    });
    if (i == m - 1) {
        return Stream.of(arr1, arr2, arr3);
    } else {
        return Stream.of(arr1, arr2);
    }
}).flatMap(Function.identity())
        .map(row -> String.join("", row))
        .toArray(String[]::new);

// output
Arrays.stream(arr).forEach(System.out::println);

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

Answer 6

You can represent a staircase as a 2d array of zeros and ones like this:

[0, 0, 0, 0, 0, 1]
[0, 0, 0, 0, 1, 1]
[0, 0, 0, 1, 1, 1]
[0, 0, 1, 1, 1, 1]
[0, 1, 1, 1, 1, 1]
[1, 1, 1, 1, 1, 1]

Then you can represent non-empty cells of this array as an almost square , consisting of two rows: a row with an upper border and a row with a left border . Empty cells are just two rows of spaces of the same length.

+---
|   

Then you can concatenate the cells of each row into one line, and output them line by line. Result consists of two parts: rows of a 2d array with a right border and a lower border row:

n=6
                    +---+
                    |   |
                +---+---+
                |   |   |
            +---+---+---+
            |   |   |   |
        +---+---+---+---+
        |   |   |   |   |
    +---+---+---+---+---+
    |   |   |   |   |   |
+---+---+---+---+---+---+
|   |   |   |   |   |   |
+---+---+---+---+---+---+

Try it online!

int n = 6;
// 2d array of zeros and ones
int[][] field = IntStream.range(0, n)
        .mapToObj(i -> IntStream.range(0, n)
                .map(j -> i + j < n - 1 ? 0 : 1)
                .toArray())
        .toArray(int[][]::new);

String[] staircase = Stream.concat(
        // rows of a 2d array with a right border
        Arrays.stream(field)
                .map(row -> IntStream.range(0, n)
                        .mapToObj(i -> new String[]{
                                // upper row of square with an upper border
                                row[i] == 0 ? "    " : "+---"
                                        // add a right border to the last element
                                        + (i < n - 1 ? "" : "+"),
                                // lower row of square with a left border
                                row[i] == 0 ? "    " : "|   "
                                        // add a right border to the last element
                                        + (i < n - 1 ? "" : "|")})
                        // reduce Stream<String[]> to a single array String[]
                        .reduce((arr1, arr2) -> IntStream.range(0, 2)
                                .mapToObj(j -> arr1[j] + arr2[j])
                                .toArray(String[]::new))
                        .orElse(new String[]{}))
                .flatMap(Arrays::stream),
        // lower border row
        Stream.of(IntStream.range(0, n)
                .mapToObj(i -> "+---" + (i < n - 1 ? "" : "+"))
                .collect(Collectors.joining())))
        .toArray(String[]::new);

// output
System.out.println("n=" + n);
Arrays.stream(staircase).forEach(System.out::println);

---

^{See also: Best way to make a border for a 2D array?}