Assignment 6 for CSCI 201

Description:

In this assignment, your last assignment this semester, you will write one program that uses arrays. This program must be turned in by 4:00 PM on Thursday, 10 December. No late assignments will be accepted.

Program 1:

(worth 25 points)

In this program you will test the random number generator of C++. You do this by generating a large uniformally distributed sequence of integers between 0 and 19 and recording the frequency with which each of these numbers occurs. You will use a histogram stored in an array of twenty integers to accomplish this task.

Let's assume you have declared H to be your histogram array. The top-level design of your program should consist of a while loop that does something like:

Prompts for the number of random integers to be generated and exits the loop if the number zero is entered.
Clears out the array H by setting all its elements to zero.
Enters a for loop that:
- Generates a random number r,
- Adds one to the r'th element of H.
Enters a for loop from 0 to 19 that:
- Print a lines that displays the number of times a particular integer was generated.

Here's a sample run of a program that solves this problem:

Enter number of randoms to generate
2000
 0:     83    ************
 1:     93    **************
 2:     91    **************
 3:    110    *****************
 4:    107    ****************
 5:     97    ***************
 6:    107    ****************
 7:     99    ***************
 8:     91    **************
 9:     98    ***************
10:     98    ***************
11:     87    *************
12:    113    *****************
13:    108    ****************
14:    105    ****************
15:     94    **************
16:    110    *****************
17:    104    ****************
18:    103    ***************
19:    102    ***************

Enter number of randoms to generate
0

The tricky parts

You may find the generation of those pretty output lines to be a challenge.

Big hint 1

First of all, you will need to use output formatting operations to make sure that your columns are lined up evenly. The output lines in the sample program were generated by a C++ statement that starts with

	  cout << setw(2) << i 
	       << ":" << setw(7) << H[i]

Big hint 2

You'll need to use a for loop to generate the right number of asterisks in your output. The tricky part is figuring out how many asterisks to generate. The sample program contains the following line:

	  m = ( H[i] * 300 + n/2) / n ;

to do this computation. In the formula above, n is the total number of random numbers that were generated, and m is the number of asterisks to be printed for H[i].

An Even Bigger hint

Below is a skeleton for the program that you need to write. This skeleton contains the complete segment of code needed to print the histogram.


int main()
{

    while (  ) {

	srand((unsigned int) time(0)) ;  //seed the random number generator


	
	for (i=0; i<20; ++i) {           // loop used to print the histogram
	    cout << setw(2) << i 
		 << ":" << setw(7) << H[i] << "  ";
	    
	    m = ( H[i] * 300 + n/2) / n ; // number of *'s to be printed
	    for (j=0; j<m; ++j)
		cout << '*' ;
	    cout << endl ;               // end of loop used to print the histogram
	}

    }  // end of while loop
    return 0 ;
}  // end of main

What to turn in:

You should turn in a floppy disk containing the source code for the program described above either on the last day of class before the final exam or in Robinson 221 before 4:00 PM on Thursday, 10 December. The disk should be labeled (on the outside) with your name and section number. The disk should contain either a cleaned workspace for this assignment or you can turn in just the C++ source code described above. Either format will be accepted.