CISC105 Fall 2006 Lab09

• Write a program or webpage for each of the following problems. Be sure to save every separate program. All programs must be properly commented and indented (see Assignment Standards on the class website).
  
  
• Exam questions often come from labs and projects. Projects and labs are frequently the source of exam questions. Frequently derived from labs and projects, exam questions are. Hard to read, this is.
  
  
• Name each program lab09.n.c, where n is the number in the list below. For example, the name of the file for the first will be lab09.1.c. Put the files in your lab09 directory.
  
  

Programs

1. Use the rand() function to generate a data file of 10,000 integers between 0 and 99, inclusive. In the data file, put ten integers on each line.
   
   
2. How random is rand()? Count the number of occurrences of each integer in the data file from the previous problem, as follows.
   1. Create an array of ints, size 100. This will hold the count of each number, e.g. index 7 will hold the number of sevens in the file.
      
      
   2. Read the data from the file with a loop; as each number is read, go to the corresponding index of the count array and increment the value there by one.
      
      
   
   
   
3. Alter the program from 2 so that it takes the name of the data file as a command line argument.
   
   
4. Create a 2d array of char to hold the words "grey", "green", and "greasy".
   1. Show how to change the first 'e' in "green" to a 'y' (hint: do not use a function to do this).
      
      
   2. Show how to print the third word.
      
      
   3. Then show how to use printf to print only the word "easy" without making changes to the array (hint: remember that when using %s printf wants an address argument).
      
      
   4. Finally, show how to replace the word "grey" with the word "great" (hint: use a function!).
      
      
   
   
   
5. Write a function that will search an array of integers of any size for a given key by traversing the array (this is called "linear search"). Your function should return the index where the key is found, as soon as it is found, or -1 if it doesn't find the key. Demonstrate your program, giving typical and boundary cases.
   
   
6. Create an array of 300 integers, and initialize the array to the values 0 - 299. Write a loop that calls your linear search function 10,000 times to find a randomly generated key. Eliminate print statements from your program. Include the header file time.h and put a call to

   srand(time(NULL));
   
   

   at the start of your main() so that the random sequence is different each time. Time your program as follows:

   > time a.out
   1.20u 0.00s 0:01.23 98.3%
   
   

   This is a use of the Unix time function. The first number is the number we care about: the amount of time we used the CPU.
   Do this three times.
   
   
7. Repeat the last experiment using the binary search function we wrote in class.