CSCI 101: Fundamentals of Computer Programming Lab 11: Strings & Sorts Fall 2005

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1 CSCI 101: Fundamentals of Computer Programming Lab 11: Strings & Sorts Fall 2005 Project #1 You are going to try running the proj1solution file from the website during the lab to ensure that you are able to do so. To execute the file, do the following: a) Download the proj1solution file from the website a. Right click on the proj1solution link and select Save Target As b. Change the Save as Type to All Files c. Make sure the filename is selected as proj1solution d. Save the file to your desktop b) In your LabLaunch, run CoreFTP. a. Connect to your aludra account by typing in your username and password b. A window will then pop up asking if you would like to save the key. Click Yes. c) Transfer the proj1solution to your account a. Go to your desktop on the left panel of the CoreFTP program b. Go to the directory on the right panel where you wish to store the proj1solution file. c. Drag the file from the left panel to the right. This will initiate the transfer. d) Running the sample solution a. Once you are done transferring, go to the directory where you store the file in your aludra account. b. Type in chmod 700 proj1solution to change the permissions on the file c. Type in proj1solution to run the program Your TA/LA will then demonstrate to you how the program should work. Strings There are no string datatypes defined in C, and thus it is simulated using character arrays. However, traditional operators such as the assignment operator =, addition operator +, comparisons >, <, >= and so will not work on arrays. This is inconvenient as we often come across situations when we would like to perform those operations. The string.h header file provides an array of predefined functions that simulates such operations on strings. The table below describes the more frequently used functions. More information can be found at:

2 char s1[10] = string 1 ; char s2[10] = string 2 ; char s3[10]; Assignment strcpy(s3, string 3 ); S3 = string 3 Concatenation strcat(s3, concatenated ); S3 = string 3 concatenated Comparison <0 if s1 < s2, 0 if s1 = s2, >0 if s1 > s2 Table of functions in string.h strcmp(s1, s2); The sample program below should clearly illustrate the use of these three functions. Note that you would need to include the string.h header file at the top of your program. You may download this program at #include <string.h> #include <stdio.h> int main(){ char name1[20]; char name2[20]; int val; printf("\nnames after initialization: \n"); strcpy(name1, "Mary"); strcpy(name2, "Arthur"); printf("\nnames after assignment: \n"); strcat(name1, " Jane"); strcat(name2, " Doyle"); printf("\nnames after concatenation: \n"); val = strcmp(name1, name2); printf("\ncomparison between name1 & name2: \n"); printf("val = %d\n", val); return 0;

3 Sorting techniques After the introduction of arrays, large amounts of data can now be stored and accessed conveniently. However, as the amount of data increases, so does the complexity in managing them. To ease this process, sorting techniques need to be introduced. You have learnt three types sorting techniques introduced by Professor Ghyam during lecture: bubble sort, insertion sort and selection sort. These three sorting techniques are generally rather intuitive and easy to implement. However, the efficiency is compromised as they are slower than other sorting techniques that are marginally harder and less intuitive. Due to time constraints, we will only familiarize ourselves with the bubble sort. Like its name sake, bubble sort is a sorting technique that bubbles up the smallest number in an array. It compares two adjacent elements, and swaps them if it is in the wrong order. The java applet at should clearly illustrate this. Feel free to try out the other sorting algorithms (especially insertion and selection sort). The program below is an example of how bubble sort is implemented. You may download it at Make sure you understand and able to visualize how the sorting technique works.

4 #include <stdio.h> int main(){ const int size = 10; int array[size]; int i, j, temp; // Initializing and printing out an unsorted array printf("\nunsorted array: "); array[i] = rand() % 50; printf(" %d", array[i]); // Sorting the array // One run of the sort for (j=1; j<size; j++){ if(array[j-1] > array[j]){ temp = array[j]; array[j] = array[j-1]; array[j-1] = temp; // Printing out the array after every run of the sort printf("\nrun %2d : ", i + 1); for (j=0; j<size; j++){ printf(" %2d", array[j]); // Printing out the final sorted array printf("\nsorted array: "); printf(" %d", array[i]); printf("\n\n"); return 0;

5 Exercise For this week s lab exercise, you will incorporate both the functions from string.h as well as bubble sort to sort a small information database. Download the database file from There are three columns of data, where the first column corresponds to the first name, the second the last name, and the third the ID of the person. You are to write a program that does the following: a) Scans all the data from the file into appropriate data structures b) Prompt the user on how he/she wants the information sorted (by first name, last name or ID) c) Sorts the data according to the request and prints the sorted database out in a legible manner. Your TA/LA will show you a sample output for this exercise. Once you are done, show your TA/LA your completed program for lab credit. Feel free to implement additional features on your program.