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Thinking in C++ Vol 2 - Practical Programming
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Solutions to selected exercises can be found in the electronic document The Thinking in C++ Volume 2 Annotated Solution Guide, available for a small fee from

1.      Create a generator that returns the current value of clock( ) (in <ctime>). Create a list<clock_t>, and fill it with your generator using generate_n( ). Remove any duplicates in the list and print it to cout using copy( ).

2.      Using transform( ) and toupper( ) (in <cctype>), write a single function call that will convert a string to all uppercase letters.

3.      Create a Sum function object template that will accumulate all the values in a range when used with for_each( ).

4.      Write an anagram generator that takes a word as a command-line argument and produces all possible permutations of the letters.

5.      Write a sentence anagram generator that takes a sentence as a command-line argument and produces all possible permutations of the words in the sentence. (It leaves the words alone and just moves them around.)

6.      Create a class hierarchy with a base class B and a derived class D. Put a virtual member function void f( ) in B such that it will print a message indicating that B s f( ) was called, and redefine this function for D to print a different message. Create a vector<B*>, and fill it with B and D objects. Use for_each( ) to call f( ) for each of the objects in your vector.

7.      Modify FunctionObjects.cpp so that it uses float instead of int.

8.      Modify FunctionObjects.cpp so that it templatizes the main body of tests so you can choose which type you re going to test. (You ll have to pull most of main( ) out into a separate template function.)

9.      Write a program that takes an integer as a command line argument and finds all of its factors.

10.    Write a program that takes as a command-line argument the name of a text file. Open this file and read it a word at a time (hint: use >>). Store each word into a vector<string>. Force all the words to lowercase, sort them, remove all the duplicates, and print the results.

11.    Write a program that finds all the words that are in common between two input files, using set_intersection( ). Change it to show the words that are not in common, using set_symmetric_difference( ).

12.    Create a program that, given an integer on the command line, creates a factorial table of all the factorials up to and including the number on the command line. To do this, write a generator to fill a vector<int>, and then use partial_sum( ) with a standard function object.

13.    Modify CalcInventory.cpp so that it will find all the objects that have a quantity that s less than a certain amount. Provide this amount as a command-line argument, and use copy_if( ) and bind2nd( ) to create the collection of values less than the target value.

14.    Use UrandGen( ) to generate 100 numbers. (The size of the numbers does not matter.) Find which numbers in your range are congruent mod 23 (meaning they have the same remainder when divided by 23). Manually pick a random number yourself, and determine whether that number is in your range by dividing each number in the list by your number and checking if the result is 1 instead of just using find( ) with your value.

15.    Fill a vector<double> with numbers representing angles in radians. Using function object composition, take the sine of all the elements in your vector (see <cmath>).

16.    Test the speed of your computer. Call srand(time(0)), then make an array of random numbers. Call srand(time(0)) again and generate the same number of random numbers in a second array. Use equal( ) to see if the arrays are the same. (If your computer is fast enough, time(0) will return the same value both times it is called.) If the arrays are not the same, sort them and use mismatch( ) to see where they differ. If they are the same, increase the length of your array and try again.

17.    Create an STL-style algorithm transform_if( ) following the first form of transform( ) that performs transformations only on objects that satisfy a unary predicate. Objects that don t satisfy the predicate are omitted from the result. It needs to return a new end iterator.

18.    Create an STL-style algorithm that is an overloaded version of for_each( ) which follows the second form of transform( ) and takes two input ranges so it can pass the objects of the second input range a to a binary function that it applies to each object of the first range.

19.    Create a Matrix class template that is made from a vector<vector<T> >. Provide it with a friend ostream& operator<<(ostream&, const Matrix&) to display the matrix. Create the following binary operations using the STL function objects where possible: operator+(const Matrix&, const Matrix&) for matrix addition, operator*(const Matrix&, const vector<int>&) for multiplying a matrix by a vector, and operator*(const Matrix&, const Matrix&) for matrix multiplication. (You might need to look up the mathematical meanings of the matrix operations if you don t remember them.) Test your Matrix class template using int and float.

20.    Using the characters
"~`!@#$%^&*( )_-+=}{[]|\:;"'<.>,?/",
generate a codebook using an input file given on the command line as a dictionary of words. Don t worry about stripping off the non-alphabetic characters nor worry about case of the words in the dictionary file. Map each permutation of the character string to a word such as the following:
"=')/%[}]|{*@?!"`,;>&^-~_:$+.#(<\" apple
"|]\~>#.+%(/-_[`':;=}{*"$^!&?),@<" carrot
"@=~['].\/<-`>#*)^%+,";&?!_{:|$}(" Carrot

Make sure that no duplicate codes or words exist in your code book. Use lexicographical_compare( ) to perform a sort on the codes. Use your code book to encode the dictionary file. Decode your encoding of the dictionary file, and make sure you get the same contents back.

21.      Using the following names:

Jon Brittle

Jane Brittle

Mike Brittle

Sharon Brittle

George Jensen

Evelyn Jensen

Find all the possible ways to arrange them for a wedding picture.

22.      After being separated for one picture, the bride and groom decided they wanted to be together for all of them. Find all the possible ways to arrange the people for the picture if the bride and groom (Jon Brittle and Jane Brittle) are to be next to each other.</#><#TIC2V2_CHAPTER8_I350>

23.      A travel company wants to find out the average number of days people take to travel from one end of the continent to another. The problem is that in the survey, some people did not take a direct route and took much longer than is needed (such unusual data points are called outliers ). Using the following generator, generate travel days into a vector. Use remove_if( ) to remove all the outliers in your vector. Take the average of the data in the vector to find out how long people generally take to travel.


int travelTime() {

// The "outlier"

if(rand() % 10 == 0)

return rand() % 100;

// Regular route

return rand() % 10 + 10;



24.    Determine how much faster binary_search( ) is to find( ) when it comes to searching sorted ranges.</#><#TIC2V2_CHAPTER8_I354>

25.      The army wants to recruit people from its selective service list. They have decided to recruit those that signed up for the service in 1997 starting from the oldest down to the youngest. Generate an arbitrary amount of people (give them data members such as age and yearEnrolled) into a vector. Partition the vector so that those who enrolled in 1997 are ordered at the beginning of the list, starting from the youngest to the oldest, and leave the remaining part of the list sorted according to age.

26.    Make a class called Town with population, altitude, and weather data members. Make the weather an enum with { RAINY, SNOWY, CLOUDY, CLEAR }. Make a class that generates Town objects. Generate town names (whether they make sense or not it doesn t matter) or pull them off the Internet. Ensure that the whole town name is lower case and there are no duplicate names. For simplicity, we recommend keeping your town names to one word. For the population, altitudes, and weather fields, make a generator that will randomly generate weather conditions, populations within the range [100 to 1,000,000) and altitudes between [0, 8000) feet. Fill a vector with your Town objects. Rewrite the vector out to a new file called Towns.txt.

27.    There was a baby boom, resulting in a 10% population increase in every town. Update your town data using transform( ), rewrite your data back out to file.

28.    Find the towns with the highest and lowest population. For this exercise, implement operator< for your Town class. Also try implementing a function that returns true if its first parameter is less than its second. Use it as a predicate to call the algorithm you use.

29.    Find all the towns within the altitudes 2500-3500 feet inclusive. Implement equality operators for the Town class as needed.

30.    We need to place an airport in a certain altitude, but location is not a problem. Organize your list of towns so that there are no duplicate (duplicate meaning that no two altitudes are within the same 100 ft range. Such classes would include [100, 199), [200, 199), etc. altitudes. Sort this list in ascending order in at least two different ways using the function objects in <functional>. Do the same for descending order. Implement relational operators for Town as needed.

31.    Generate an arbitrary number of random numbers in a stack-based array. Use max_element( ) to find the largest number in array. Swap it with the number at the end of your array. Find the next largest number and place it in the array in the position before the previous number. Continue doing this until all elements have been moved. When the algorithm is complete, you will have a sorted array. (This is a selection sort .)

32.    Write a program that will take phone numbers from a file (that also contains names and other suitable information) and change the numbers that begin with 222 to 863. Be sure to save the old numbers. The file format is as follows:

222 8945

756 3920

222 8432


33.    Write a program that, given a last name, will find everyone with that last name with his or her corresponding phone number. Use the algorithms that deal with ranges (lower_bound, upper_bound, equal_range, etc.). Sort with the last name acting as a primary key and the first name acting as a secondary key. Assume that you will read the names and numbers from a file where the format will be as follows. (Be sure to order them so that the last names are ordered, and the first names are ordered within the last names.):


John Doe 345 9483

Nick Bonham 349 2930

Jane Doe 283 2819


34.    Given a file with data similar to the following, pull all the state acronyms from the file and put them in a separate file. (Note that you can t depend on the line number for the type of data. The data is on random lines.)
















When complete, you should have a file with all the state acronyms which are:


35.    Make an Employee class with two data members: hours and hourlyPay. Employee shall also have a calcSalary( ) function which returns the pay for that employee. Generate random hourly pay and hours for an arbitrary amount of employees. Keep a vector<Employee*>. Find out how much money the company is going to spend for this pay period.

36.    Race sort( ), partial_sort( ), and nth_element( ) against each other and find out if it s really worth the time saved to use one of the weaker sorts if they re all that s needed.



Thinking in C++ Vol 2 - Practical Programming
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   Reproduced courtesy of Bruce Eckel, MindView, Inc. Design by Interspire