C++ Primer Plus

8. Why didn’t the STL designers simply define a base iterator class, use inheritance to derive classes for the other iterator types, and express the algorithms in terms of those iterator classes?

9. Give at least three examples of convenience advantages that a vector object has over an ordinary array.

10. If Listing 16.9 were implemented with list instead of vector, what parts of the program would become invalid? Could the invalid part be fixed easily? If so, how?

11. Consider the TooBig functor in Listing 16.15. What does the following code do, and what values get assigned to bo?

bool bo = TooBig(10)(15);

Programming Exercises

1. A palindrome is a string that is the same backward as it is forward. For example, “tot” and “otto” are rather short palindromes. Write a program that lets a user enter a string and that passes to a bool function a reference to the string. The function should return true if the string is a palindrome and false otherwise. At this point, don’t worry about complications such as capitalization, spaces, and punctuation. That is, this simple version should reject “Otto” and “Madam, I’m Adam.” Feel free to scan the list of string methods in Appendix F for methods to simplify the task.

2. Do the same problem as given in Programming Exercise 1 but do worry about complications such as capitalization, spaces, and punctuation. That is, “Madam, I’m Adam” should test as a palindrome. For example, the testing function could reduce the string to “madamimadam” and then test whether the reverse is the same. Don’t forget the useful cctype library. You might find an STL function or two useful although not necessary.

3. Redo Listing 16.3 so that it gets it words from a file. One approach is to use a vector object instead of an array of string. Then you can use push_back() to copy how ever many words are in your data file into the vector object and use the size() member to determine the length of the word list. Because the program should read one word at a time from the file, you should use the >> operator rather than getline(). The file itself should contain words separated by spaces, tabs, or new lines.

4. Write a function with an old-style interface that has this prototype:

int reduce(long ar[], int n);

The actual arguments should be the name of an array and the number of elements in the array. The function should sort an array, remove duplicate values, and return a value equal to the number of elements in the reduced array. Write the function using STL functions. (If you decide to use the general unique() function, note that it returns the end of the resulting range.) Test the function in a short program.

5. Do the same problem as described in Programming Exercise 4, except make it a template function:

template

int reduce(T ar[], int n);

Test the function in a short program, using both a long instantiation and a string instantiation.

6. Redo the example shown in Listing 12.12, using the STL queue template class instead of the Queue class described in Chapter 12.

7. A common game is the lottery card. The card has numbered spots of which a certain number are selected at random. Write a Lotto() function that takes two arguments. The first should be the number of spots on a lottery card, and the second should be the number of spots selected at random. The function should return a vector object that contains, in sorted order, the numbers selected at random. For example, you could use the function as follows:

vector winners;

winners = Lotto(51,6);

This would assign to winners a vector that contains six numbers selected randomly from the range 1 through 51. Note that simply using rand() doesn’t quite do the job because it may produce duplicate values. Suggestion: Have the function create a vector that contains all the possible values, use random_shuffle(), and then use the beginning of the shuffled vector to obtain the values. Also write a short program that lets you test the function.

8. Mat and Pat want to invite their friends to a party. They ask you to write a program that does the following:

• Allows Mat to enter a list of his friends’ names. The names are stored in a container and then displayed in sorted order.

• Allows Pat to enter a list of her friends’ names. The names are stored in a second container and then displayed in sorted order.