Solution to question 0

import java.util.Scanner;

/* YOUR NAME  Loop Hwk #1 Comp 110
 * Assigned: Mon 2/21
 * Due: Fri 2/5 at start of lab
 * You may work together on these problems, but each student
 * must turn in their solution on Sakai.
 * This homework is just practice writing loops in Java.
 * You do not need an Implementation Plan or a Test Plan.
 * Just complete the Java code for each of the methods.
 */

public class LoopFeb18SOLUTION {
	
	public static void main( String[] args) {
		
		// Change the name of this method (e.g. question1) to 
		// run your code for a different question on this assignment.
		question0v2();
	}
	
	/* 
	 * Ask the user to "Enter a positive integer"
	 * Print out the sum of the first n odd integers
	 * where n is the number entered by the user.
	 * For example, if the user enters 5, print out
	 * 25 = 1 + 3 + 5 + 7 + 9
	 */
	public static void question0() {
	   Scanner keyboard = new Scanner(System.in);
	   System.out.println("Enter a positive integer");
	   int n = keyboard.nextInt();

	   // Put your code here
	}
	
	
	/*
	 * Step 1 - understand the problem
	 * Step 2 - Make it concrete. Pick a typical input.
	 *     Draw your data (not applicable on question0).
	 *     
	 * We use as the typical input the example given in
	 * the problem.
	 * n = 5
	 * 1 + 3 + 5 + 7 + 9 = 25
	 * 
	 * Step 3 - write a loop that executes the correct number
	 * of times (but does nothing useful).
	 */
	public static void question0v0() {
		   Scanner keyboard = new Scanner(System.in);
		   System.out.println("Enter a positive integer");
		   int n = keyboard.nextInt();

		   int count = 0;
		   while( count <= n ) {
			   System.out.println("count = " + count);
			   count++;
		   }
		   System.out.println("count = " + count);
		}
	
	/* Whoops - an off by one error.  This is a very common
	 * mistake to make.  We fix the loop and sum up n
	 * values. Not yet sure how to get only the odd numbers.
	 * First, we will just sum up ones.
	 */
	public static void question0v1() {
		   Scanner keyboard = new Scanner(System.in);
		   System.out.println("Enter a positive integer");
		   int n = keyboard.nextInt();

		   // To fix the loop, either initialize to 1 (not 0)
		   // or change the condition to less than (not <=).
		   // Its doesn't matter which you do.
		   int count = 0;
		   
		   int sum = 0;  // new code
		   
		   while( count < n ) { 
			   System.out.println("count = " + count);
			   
			   sum = sum + 1;  // new code
			   
			   count++;
		   }
		   System.out.println("count = " + count);
		   System.out.println("sum = " + sum);
		}
	
	/* 
	 * Last step - compute the odd integers. It helps to line up
	 * the value of count with the integer we want to add.
	 * 
	 * 0 1 2 3 4
	 * 1 3 5 7 9
	 * 
	 * What is the pattern? How do we take the number in the first
	 * row and compute the corresponding number in the second row?
	 */
	
	public static void question0v2() {
		   Scanner keyboard = new Scanner(System.in);
		   System.out.println("Enter a positive integer");
		   int n = keyboard.nextInt();

		   // To fix the loop, either initialize to 1 (not 0)
		   // or change the condition to less than (not <=).
		   // Its doesn't matter which you do.
		   int count = 0;	   
		   int sum = 0;
		   
		   while( count < n ) { 
			   System.out.println("count = " + count);
			   
			   sum = sum + 2*count + 1;  // new code			   
			   count++;
		   }
		   System.out.println("count = " + count);
		   System.out.println("sum = " + sum);
		}
}