CSCI 102 Fall 2010 Exam #1

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1 Name: USC Username: CSCI 102 Fall 2010 Exam #1 Problems Problem #1 (14 points) Problem #2 (15 points) Problem #3 (20 points) Problem #4 (16 points) Problem #5 (35 points) Total (100 points)

2 Problem 1 Short Answer (14 points) Give a brief answer to each of the following questions (a couple sentences usually suffices). Feel free to add drawings or pseudocode if you think it will help you get your point across. 1A (3 points). What is the purpose of namespaces in C++? 1B (3 points). Explain what each of the the keywords public, private and protected mean inside a class declaration. 1C (4 points). What is the purpose of the C++ keywords new and delete? 1D (4 points). What is the difference between object composition and object inheritance? Explain and give a brief example of each.

3 Problem 2 Argument Passing (15 points) A CS 101 student has written the following code to increment a variable: void increment(int x) x++; int main() int num = 5; cout << Before = << num << endl; increment(num); cout << After = << num << endl; The student wants the increment function to change the value of num in main, but currently their code always prints out the value of 5 for num before and after the call to increment(num). 2A (3 points). Why doesn't the student's code change the value of num when calling increment(num)? 2B (6 points). Show how you would modify the student's code using pass by reference so that the value of num is changed after the call to increment(num) (you don't have to rewrite all the code, just rewrite the lines that need to change or the lines you want to add). 2C (6 points). Show how you would modify the student's code using pass by pointer so that the value of num is changed after the call to increment(num) (you don't have to rewrite all the code, just rewrite the lines that need to change or the lines you want to add).

4 Problem 3 User Input Validation (20 points) The following pieces of code prompt the user to enter an integer, read it in from the console, and then display it back to the console. It works great when the user is well-behaved and enters a number, but it doesn't work correctly if the user enters something like asdf. Correct the code so it gracefully handles bad input and re-prompts the user for a good value. Don't worry about fringe cases like 33asdf or Ctrl-D, just handle basic non-numeric input like asdf. 3A (10 points). Correct the code by using the cin.fail() method of checking the user's input. Don't worry about #include or using statements, just write the code that matters. int main() int x; cout << "Enter X: "; cin >> x; cout << "X = " << x << endl;

5 3B (10 points). Correct the code by using C++ exception handling to check the user's input (don't use cin.fail()). We've provided you with the statement to cause cin to throw exceptions. Don't worry about #include or using statements, just write the code that matters. int main() cin.exceptions( iostream::failbit ); int x; cout << "Enter X: "; cin >> x; cout << "X = " << x << endl;

6 Problem 4 Classes and Inheritance (16 points) You are given the following class definitions: class Shape protected: Point center; public: Shape(Point p) : center(p) Point getcenter() const return center; void setcenter(point p) center = p; void print() const cout << I am an instance of Shape! << endl; ; class Circle : public Shape protected: double radius; public: Circle(Point p,double rad); double getradius() const return radius; void setradius(double rad) radius = rad; ; 4A (4 points). Write the implementation of the provided constructor for the Circle class.

7 4B (6 points). Make any modifications necessary to Shape and Circle to make it so the Circle class overrides the print() method in Shape. This includes implementing the print() function in Circle; make it print out whatever you like. Make sure that if the following code was run, it would call Circle's print() method, not Shape's: Shape *s = new Circle(); s->print(); 4C (6 points). Make a pure virtual function double getperimeter() in the Shape class and override it in your Circle class (this includes implementing the getperimeter() function in Circle). Remember that a circle's perimeter is equal 2 * 3.14 * radius.

8 Problem 5 Input/Output (35 points) You are required to write the code for a full, functioning C++ application to perform the following task: The Galen Center is having trouble keeping track of their sales of refreshments. As a work-study and CS student, you ve been given the task of writing the program to keep track of their total sales. The problem is that the people doing the actual sales are not very good at typing. They might enter invalid data at any time. For each sale, they have to enter the numeric type of the drink that was purchased (1 through 3) and the quantity of that type of drink that was purchased (a positive integer). There are 3 types of drinks that are sold: 1) Water - $1.00 2) Soda - $2.00 3) Juice - $3.00 There are no returns, so the quantity of a drink that can be sold can never be negative. Notice that the price of each drink is its numeric type in dollars (e.g. water is item 1 and is $1.00). Your program is to prompt the cashier for drink type and quantity (in a loop!) until the cashier enters zero for the drink type (if the drink type is zero, you can break your loop immediately or read in the quantity and just ignore it). When the user enters 0 for the drink type, you should print out a line to the console for each type of drink that includes the total number of each drink sold and the total sales (in dollars) for that type of drink. The last line is the total sales for all drinks (the total amount of money). No pretty formatting necessary. Don't worry about #include or using statements, just write the code that matters. You should ignore any bad data. If you receive bad data, just re-prompt the user for the values again. You can refer to your code from Problem 3 as a function if you want (i.e. you don't have to rewrite all the logic that you wrote in Problem 3 for validating reading in an integer from the console). The next page is blank if you need more room to write...

CSCI 101L - Data Structures. Practice problems for Final Exam. Instructor: Prof Tejada

CSCI 101L - Data Structures. Practice problems for Final Exam. Instructor: Prof Tejada CSCI 101L - Data Structures Practice problems for Final Exam Instructor: Prof Tejada 1 Problem 1. Debug this code Given the following code to increase the value of a variable: void Increment(int x) { x