使用嵌套的循环绘制圣诞树

Question

I am trying to draw christmas trees that would look something like this in the console, depending on the height the user enters in. here are the rules. Top part: The rectangle/triangle has as many rows as the number the user entered. The width of the rectangle/triangle is one less than twice the height of the tree (for example, the tree of height 5 has a width of 9). In the case of triangle, the base of the top part is right up against the left margin, and each line above it is indented one space further, and is two characters shorter. The result is an isosceles triangle that looks a bit like the top of a spruce or fir tree. Bottom part: The rectangle below is centred under the rectangle (for Flat tree) or triangle (for Xmas tree). Its height is one more than one fifth of the height of the top part. For example, the rectangle of the tree above has two rows, since 9 ÷ 5 + 1 is 2. The width of the rectangle is one third of the width of the tree -- but add one if that width comes out even. For example, the triangle of height 5 has a width of 9, so the width of the rectangle is 3 (that's 9 ÷ 3). The tree of height 4, however, has a base of width 7. Its rectangle would be 3 wide (ie, 7 ÷ 3 is 2, which is even, so change it to 3).

How tall should the top of the tree be? 7
Flat Tree:
*************
*************
*************
*************
*************
*************
*************
    *****
    *****
Xmas Tree:
      *
     ***
    *****
   *******
  *********
 ***********
*************
    *****
    *****

At the moment this is my code, TreeStructures.java

import java.util.Scanner;

public class TreeStructures {

public static void main(String[] args) {
    Scanner scnr = new Scanner(System.in);
    int height;
    System.out.print("How tall should the top of the tree be? ");
    height = scnr.nextInt();
    int topWidth = (height * 2) - 1;
    int bottomWidth = topWidth/3;
    System.out.println();
    if (height >= 5 && height <= 20) {
        if(bottomWidth % 2 == 0) {
            bottomWidth = (topWidth/3) + 1;
        }
        // FLAT TREE -----------------------------------------
        System.out.println("Flat tree:");
        // first for loop to print number of rows
        for (int i = 1; i <= height; i++) {
            // second for loop to print stars to create rectangle
            for (int stars = 1; stars <= topWidth; stars++) {
                System.out.print("*");
            }
            // println to print rows in.
            System.out.println();
        }
        // first for loop to print out rows for the bottom part of tree
        for (int i = 0; i <= (height / 5) + 1; i++) {
            // for loop to print the bottom part of the tree
            for (int j = 0; j <= bottomWidth - 1; j++) {
                System.out.print(" ");
            }
            for (int j = 0; j <= bottomWidth - 1; j++) {
                System.out.print("*");
            }
            System.out.println();
        }

        // XMAS TREE --------------------------------------------
        System.out.println("Xmas tree:");
        // NESTED LOOPS
        // first for loop to print amount of rows
        for (int i = 0; i < height; i++) {
            // second for loop for print out spaces to match the tree level
            for (int j = 1; j < height - i; j++) {
                System.out.print(" ");
            }
            // third for loop to print out stars
            for (int k = 0; k < (2 * i + 1); k++) {
                System.out.print("*");
            }
            System.out.println();
        }
        // first for loop to determine amount of rows for bottom
        for (int i = 0; i <= (height / 5); i++) {
            // for loop to print the bottom part of the tree
            for (int j = 0; j <= bottomWidth - 1; j++) {
                System.out.print(" ");
            }
            for (int j = 0; j <= bottomWidth - 1; j++) {
                System.out.print("*");
            }
            System.out.println();
        }
    } else {
        System.out.println("Sorry, i can only take heights between 5 and 20"
                + "\nQuitting now...");
    }


}

}

see as of now i have the trees done, and i have the bottom part in there, but the math is off for some reason, i thought it would work but somethings up, second thing, i dont know how to add the spaces for the bottom part to be centered under the top part of the tree.

my output right now looks like this.

How tall should the top of the tree be? 8
Flat tree:
***************
***************
***************
***************
***************
***************
***************
***************
     *****
     *****
     *****
Xmas tree:
       *
      ***
     *****
    *******
   *********
  ***********
 *************
***************
     *****
     *****

but when i enter any other number like 6, 5 , 8.. the bottom isnt centered

Answer 1

As you have 1/3 for the stem the spaces on both sides are also 1/3 of the whole width. The general formula would be (width-stemWidth)/2 which results in 1/3 width in this case.

I removed the modula and replaced it by "(height -1) / 5 +1" - it rounds up to next bigger int. So if height is 1,2,3,4 or 5 it gives 1(that is including 0: 2 rows), and if height is in 6,7,8,9 or 10 it gives 2(that is including 0: 3 rows) and so on. I am not sure but thought thats what you wanted to achieve with the modula.

import java.util.Scanner;

public class TreeStructures {

    static Scanner scnr = new Scanner(System.in);
    static int height;

    public static void main(String[] args) {

        System.out.print("How tall should the top of the tree be? ");
        height = scnr.nextInt();
        System.out.println();
        if (height >= 5 && height <= 20) {
            System.out.println("Flat tree:");
            flatTree();
            System.out.println("Xmas tree:");
            xmasTree();
        } else {
            System.out.println("That's not a valid size. I can only do trees from 5 to 20");
            System.out.println("Quitting now.");
        }

    }

    public static void flatTree() {
        int width = (height * 2) - 1;
        // first for loop to print number of rows
        for (int i = 1; i <= height; i++) {
            // second for loop to print stars to create rectangle
            for (int stars = 1; stars <= width; stars++) {
                System.out.print("*");
            }
            // println to print rows in.
            System.out.println();
        }
        //first for loop to print out rows for the bottom part of tree
        for (int i = 0; i <= height / 5; i++) {
            if (height % 2 == 0) {
                for (int j = 0; j <= ((width) / 3) + 1; j++) {
                    System.out.print("*");

                }
            } else {

                //second for loop to print out width for the bottom part of the tree
                for (int j = 0; j <= (width) / 3; j++) {
                    System.out.print("*");

                }
            }
            System.out.println();
        }

    }

    public static void xmasTree() {
        int width = height * 2 - 1;
        // NESTED LOOPS
        // first for loop to print amount of rows
        for (int i = 0; i < height; i++) {
            // second for loop for print out spaces to match the tree level
            for (int j = 0; j < height - i; j++) {
                System.out.print(" ");
            }
            // third for loop to print out stars
            for (int k = 0; k < (2 * i + 1); k++) {
                System.out.print("*");
            }
            System.out.println();
        }
        // first for loop to determine amount of rows for bottom
        for (int i = 0; i <= (height-1) / 5 +1 ; i++) {
                // for loop to print the bottom part of the tree
                for (int j = 0; j <= width/3; j++) {
                    System.out.print(" ");
                }
                for (int j = 0; j <= (width) / 3; j++) {
                    System.out.print("*");
                }
                System.out.println();
        }

    }

}

output:

How tall should the top of the tree be? 10

Flat tree:
*******************
*******************
*******************
*******************
*******************
*******************
*******************
*******************
*******************
*******************
********
********
********
Xmas tree:
          *
         ***
        *****
       *******
      *********
     ***********
    *************
   ***************
  *****************
 *******************
       *******
       *******
       *******

If you want it centered nicely in any case, you need to cheat a little and vary the stem width.

To do so: We know that the tree should be like:

witdh = gap * stemwidth + gap

From that we can easily deduct, the gap is

gap = ( with-stemwidth)/2

Now inserting that again the width is:

width = ( with-stemwidth)/2 + stemwidth + ( with-stemwidth)/2

From that we can deduct:

stemwidth = witdh - 2*(( with-stemwidth)/2).

Well one could evaluate the right and show that this equation is correct.

In discrete mathematics we need to take raounding and remainders into account.

When calculating the gap a rounding happens in the division and leaves some remainder which is lost.

So with the formula above we calculate a new stemwidth that in discrete adds that lost remainder to the stemwidth again. Making it a little bigger - but centered.

public static void xmasTree() {
    int width = height * 2 - 1;
    int stem = width - 2*width/3; 
    // NESTED LOOPS
    // first for loop to print amount of rows
    for (int i = 0; i < height; i++) {
        // second for loop for print out spaces to match the tree level
        for (int j = 0; j < height - i; j++) {
            System.out.print(" ");
        }
        // third for loop to print out stars
        for (int k = 0; k < (2 * i + 1); k++) {
            System.out.print("*");
        }
        System.out.println();
    }
    // first for loop to determine amount of rows for bottom
    for (int i = 0; i <= (height - 1) / 5 + 1; i++) {
        // for loop to print the bottom part of the tree
        for (int j = 0; j <= width / 3; j++) {
            System.out.print(" ");
        }
        //here we put the formula to use, instead of using width/3, the equivalent is used, that takes rounding into account.
        for (int j = 0; j < width - 2*(width/3); j++) {
            System.out.print("*");
        }
        System.out.println();

    }