CS 1073 -- Homework 3

CS 1073 Introductory Programming
for Scientific Applications
Homework 3: Print a Tree

Due Date:

Friday, 15 October 2004, at start of class.

Overview: This homework asks you are to print a "tree" shape made up of stars, where the size of the tree can vary. For example, here are several trees of different sizes:

size = 7	size = 10	size = 15
* * *** *** ***** ******* * * * *********	* * *** *** ***** ******* ********* *********** ************* * * * *********	* * * *** ***** ******* ********* *********** ************* *************** ***************** ******************* ********************* *********************** * * * *******

size = 7

size = 10

size = 15

      *
     ***
    *****
   *******
  *********
 ***********
     ***
     ***
     ***
   *******

         *
        ***
       *****
      *******
     *********
    ***********
   *************
  ***************
 *****************
        ***
        ***
        ***
      *******

              *
             ***
            *****
           *******
          *********
         ***********
        *************
       ***************
      *****************
     *******************
    *********************
   ***********************
  *************************
 ***************************
             ***
             ***
             ***
           *******

General directions:

The main tool for this program is a function that prints any number of characters of one kind on a line, without skipping to a new line:
The following are examples:
- the call chars('*', 8); prints 8 stars in a row on a line,
- chars(' ', 5); prints 5 blanks in a row on a line.
- The calls chars('*', 0); and chars('*', -1); print nothing.
- The call chars('\n', 1); does the same as System.out.println();.
Initially just use the following to specify a tree of size 10, and change the 10 to a 15 in your program to specify a tree of size 15:

At the end, you should use the following functions and import statement (all in red to allow you to read an int that you type in. (These are shown in a simple demonstration program.)

Java Program	Three Sample runs
// DemoInput: demonstrate input import java.io.; public class DemoInput { // getNextChar: fetches next char public static char getNextChar() { char ch; try { ch = (char)System.in.read(); } catch (Exception exception) { System.out.println("Error reading character"); ch = ' '; } return ch; } // getNextInt: fetches next int. public static int getNextInt() { char ch = ' '; // = ' ' to keep compiler happy int num; // the number to convert int sign = 1; // gives sign of answer ch = getNextChar(); // skip over initial blanks and newlines while (ch == ' ' \|\| ch == '\n') ch = getNextChar(); // check for + or - sign if (ch == '+') ch = getNextChar(); if (ch == '-') { sign = -1; ch = getNextChar(); } // read digits, construct input integer; // (same as the method "Integer.parseInt()" ) num = 0; while (Character.isDigit(ch)) { num = num10 + (ch - '0'); ch = getNextChar(); } return sign * num; } public static void main (String[] args) { System.out.print("Enter integer ---> "); int demoValue = getNextInt(); while (demoValue >= 0) { System.out.println("Input value = " + demoValue); System.out.print("Enter integer ---> "); demoValue = getNextInt(); } } // end of main }	Enter integer ---> 10 Input value = 10 Enter integer ---> 5 Input value = 5 Enter integer ---> -2 Enter integer ---> -4 Enter integer ---> 3 Input value = 3 Enter integer ---> 2 Input value = 2 Enter integer ---> 1 Input value = 1 Enter integer ---> 0 Input value = 0 Enter integer ---> -1

Java Program

Three Sample runs


// DemoInput: demonstrate input
import java.io.*;
public class DemoInput {
   // getNextChar: fetches next char
   public static char getNextChar() {
      char ch;
      try {
         ch = (char)System.in.read();
      }
      catch (Exception exception) 
      {
         System.out.println("Error reading character");
         ch = ' ';
      }
      return ch;
   }

   // getNextInt: fetches next int.
   public static int getNextInt() {
      char ch = ' '; // = ' ' to keep compiler happy
      int num;  // the number to convert
      int sign = 1; // gives sign of answer
      ch = getNextChar();
      // skip over initial blanks and newlines
      while (ch == ' ' || ch == '\n')
         ch = getNextChar();
      // check for + or - sign
      if (ch == '+') ch = getNextChar();
      if (ch == '-') {
         sign = -1;
         ch = getNextChar();
      }
      // read digits, construct input integer;     
      // (same as the method "Integer.parseInt()"  )
      num = 0;
      while (Character.isDigit(ch)) {
         num = num*10 + (ch - '0');
         ch = getNextChar();
      }
      return sign * num;
   }
               
   public static void main (String[] args) {
      System.out.print("Enter integer ---> ");
      int demoValue = getNextInt();
      while (demoValue >= 0) {
         System.out.println("Input value = " + demoValue);
         System.out.print("Enter integer ---> ");
         demoValue = getNextInt();
      }
   } // end of main
}

Enter integer ---> 10
Input value = 10
Enter integer ---> 5
Input value = 5
Enter integer ---> -2

Enter integer ---> -4

Enter integer ---> 3
Input value = 3
Enter integer ---> 2
Input value = 2
Enter integer ---> 1
Input value = 1
Enter integer ---> 0
Input value = 0
Enter integer ---> -1

Here are some hints: Suppose size = 10. For the bushy part of the tree, we will want 10 rows, using a loop. For rows 1, 2, 3, ..., 10, you need to print an initial number of blanks equal to 9, 8, 7, ..., 0. You need to think of a simple expression involving the loop counter that will give these values. For every row except the 10th one, including the "trunk" and "base" of the tree, you need to output initial blanks.

What to turn in:

Source listings (the Java code) for the program.
Results of runs for trees of sizes 10, 7, 15, and 3.
Note: You should use netBeans, though it is permissible to use Java from another source. In netBeans, the simplest way to make up the material to print is to just copy from netBeans (using ctrl-C) and paste into Word or WordPad (using ctrl-V). Then print the resulting document. You can assemble all 5 programs into a single document to print.
In case you have written a program for one part, but it doesn't produce output or doesn't produce the correct output, you should still turn in a listing for part credit.

CS 1073 Introductory Programming for Scientific Applications Homework 3: Print a Tree

CS 1073 Introductory Programming
for Scientific Applications
Homework 3: Print a Tree