Homework 11: Extra Credit 3: Median

Due: Tuesday 4/24 by 11:59pm Friday May 11, 2012

Objectives

More practice with arrays.

Assignment

This assignment is a continuation of Classwork 14. (Note: you must still submit Classwork 14 and Homework 11 separately.) For this assignment you will extend your program in Classwork 14 to calculate the median score. Recall that the median score is the value x such that half of the scores are less than or equal to x and half of the scores are greater than or equal to x. (Note: if there are an even number of values, then two values might be considered the median. Just report one of these two values, do not take the average.)

For example, the median of {1, 7, 2, 2, 4, 2, 9, 3, 7} is 3 because 4 values (1, 2, 2 and 2) are less than 3 and 4 values (7, 4, 9 and 7) are greater than 3.

Notes

Make a copy of your program from Classwork 14 using the Unix cp command:
```
   cp mode.c median.c
   
```
Two test files have been prepared for you: hw11test1.txt and hw11test2.txt. The first one has 21 scores and is good for debugging. The second file has 999 scores.
It is useful to print out n just for debugging/development purposes.
Think about how to calculate the median. You already have the count[] array computed. If you iterate through the count[] array, you should be able to determine when half of the scores have been encountered. Then you have the median. Do this by hand on a small example first.

Remember to use input redirection.

   PT[351]% ./a.out <hw11test1.txt
   The number of scores is 21.
   The average score is: 13.047619
   count[0] is 0.
   count[1] is 1.
   count[2] is 2.
   count[3] is 0.
   count[4] is 0.
   count[5] is 0.
   count[6] is 0.
   count[7] is 1.
   count[8] is 1.
   count[9] is 1.
   count[10] is 0.
   count[11] is 1.
   count[12] is 2.
   count[13] is 1.
   count[14] is 0.
   count[15] is 1.
   count[16] is 2.
   count[17] is 2.
   count[18] is 1.
   count[19] is 2.
   count[20] is 3.
   The mode of the scores is 20. It occurred 3 times.
   The median score is 15.

Test your program on your own test data as well. Your myrandom() function from Homework 9 can be used to generate test data. Your program will also be tested on data other than hw11test1.txt and hw11test2.txt.

What to submit

Use the script command to record yourself compiling your program and running your program on hw11test1.txt, hw11test2.txt and any other test file that you have created. Then submit your program and typescript file as usual:


submit cs104_chang hw11 median.c typescript