Description
Objective
• Practice using the Standard Library containers, iterators, and algorithms.
1. Recall that a palindrome is a word or phrase that reads the same when read forward or
backward, such as “Was it a car or a cat I saw?”. The reading process ignores
spaces, punctuation, and capitalization.
Write a function named isPalindrome that receives a string as parameter and determines whether the received string is a palindrome.
Your implementation may not use
• any loops explicitly; that is, no for, while or do/while loops
• more than one local string object
• raw arrays, STL container classes
Use the following function to test your isPalindrome function:
void test_is_palindrome ()
{
std :: string str_i = std :: string (“Was it a car or a cat I saw?”);
std :: string str_u = std :: string (“Was it a car or a cat U saw?”);
cout << " the phrase \"" + str_i + "\" is " +
( is_palindrome ( str_i ) ? "" : "not ") + "a palindrome \n";
cout << " the phrase \"" + str_u + "\" is " +
( is_palindrome ( str_u ) ? "" : "not ") + "a palindrome \n";
}
A Suggestion:
bool is_palindrome ( const std :: string & phrase )
{
string temp ;
1. use std::remove copy if to move only alphabet characters from phrase to
temp; note that temp is empty; hence the need for an inserter iterator
2. use std::transform to convert all characters in temp to uppercase (or
lowercase) (see page 22, Smart Pointers + Move Semantics, Moodle)
3. use std::equal to compare the first half of temp with its second half,
moving forward in the first half (starting at temp.begin()) and moving
backward in the second half (starting at temp.rbegin())
4. return the outcome of step 3
}
1
2. Write a function template named second_max to find the second largest element in
a container within a given range [start, finish), where start and finish are
iterators that provide properties of forward iterators.
Your function template should be prototyped as follows, and may not use STL algorithms or containers.
template
std :: pair < Iterator ,bool > // function template return type
second_max ( Iterator start , Iterator finish ) // function signature
{
// your code
}
Clearly, in the case where the iterator range [start, finish) contains at least two
distinct objects, second_max should return an iterator to the second largest object.
However, what should second_max return if the iterator range [start, finish) is
empty or contains objects which are all equal to one another? How should it convey
all that information back to the caller?
Mimicking std::set’s insert member function, your second_max function should
return a std::pair
condition value to return
R is empty std::make_pair (finish,false)
R contains all equal elements std::make_pair (start,false)
R contains at least two distinct elements std::make_pair (iter,true)
R is the range [start, finish),
iter is an Iterator referring to the 2nd largest element in the range.
Use the following function to test your second_max function:
2
void test_second_max (std :: vector
{
// note : auto in the following statement is deduced as
// std :: pair
auto retval = second_max (vec . begin (), vec .end ());
if ( retval . second )
{
cout << "The second largest element in vec is "
<< * retval . first << endl ;
}
else
{
if ( retval . first == vec .end ())
cout << " List empty , no elements \n";
else
cout << " Container ’s elements are all equal to "
<< * retval . first << endl ;
}
}
3
3. Consider the count_if algorithm in the
function template std::count_if
template
typename iterator_traits < InputIterator >:: difference_type
count_if ( InputIterator first , InputIterator last , UnaryPredicate pred );
Returns the number of elements in the range [first,last) for which pred is true.
Write a function named countStrings that takes two parameters: a
vector
return the number of strings in the vector whose length is equal to n. Your functions must use the count_if algorithm.
For example, suppose
std :: vector
“BB”, “A”, “D”, “CC”, “DDD”, “AAA” };
Then, for example, the call countStrings(vec, 1) should return 6, the call
countStrings(vec, 3) should return 2, etc.
You should write three versions of countStrings, implementing the callable argument
to count_if as follows:
A. A lambda expression named countStringLambda
B. A free function named countStringFreeFun
C. A functor (function object) named countStringFunctor
Recall that an object or expression is callable if the call operator can be applied to it.
4
4. The STL algorithm for each accepts as parameters a range of iterators and a unary
callable, then calls the callable on each argument.
Write a function charFrequency() that reads a string of any number of characters
from the keyboard, storing and counting the frequencies of each input character (except
whitespace).
Your code must use a map
their frequency counts (values) as pair
instead, use the for_each algorithm to extract characters from the input stream and
reflect the characters and their frequency counts into the map.
Hint: although the task at hand here might seem very involved, reading input characters
and counting their frequencies can be implemented using just one statement! Simply,
implement the callable parameter of the for_each algorithm as a lambda expression,
capturing your map object into your lambda by reference.
Here is the output from a sample run:
Enter one or more lines of text .
To end input press Ctrl -Z in Windows and Ctrl -D in Linux
line one
line two
line three and no more lines after this last line .
^Z
. 1
a 3
d 1
e 10
f 1
h 2
i 6
l 6
m 1
n 8
o 4
r 3
s 3
t 5
w 1
5
5. Consider the following function that uses a multiset defined using std::multiset’s
default compare function:
1 void multisetUsingDefaultComparator ()
2 {
3 std :: multiset
4
5 // a set that uses the default std :: less
6 std :: vector
7 “BB”, “A”, “D”, “CC”, “DDD”, “AAA” };
8
9 // copy the vector elements to our set .
10 // We must use a general ( not front or back ) inserter
11 // ( set does not have push_front or push_back members ,
12 // so we can ’t use front or back inserter )
13 std :: copy (vec. begin (), vec.end(), // source container range
14 std :: inserter (strSet , strSet . begin ())); // general inserter
15
16 // create an ostream_iterator for writing to cout ,
17 // using a space ” ” as a separator
18 std :: ostream_iterator
19
20 // output the set elements to cout separating them with a space
21 std :: copy ( strSet . begin (), strSet .end(), out);
22 }
The function produces the following output:
A A A AAA B BB BB C CC CC D DDD
Modify the construction of the strSet set at line 3 so that the resulting function,
named multisetUsingMyComparator(), outputs:
A A A B C D BB BB CC CC AAA DDD
The effect is that the string elements in strSet are now ordered into groups of strings
of increasing lengths 1, 2, 3, …, with the strings in each group sorted lexicographically.
6
Test Driver Code
int main ()
{
// problem 1:
test_is_palindrome ();
cout << "\n";
// problem 2:
std :: vector
test_second_max (v1);
std :: vector
test_second_max (v2);
std :: vector
test_second_max (v3);
cout << "\n";
// problem 3:
std :: vector
{ ” count_if “, ” Returns “, “the”, ” number “, “of”, ” elements “, “in”, “the”,
” range “, “[ first “, ” last )”, “for”, ” which “, ” pred “, “is”, ” true .”
};
cout << countStringLambda (vecstr , 5) << endl ;
cout << countStringFreeFun (vecstr , 5) << endl ;
cout << countStringFunctor (vecstr , 5) << endl ;
cout << "\n";
// problem 4:
charFrequency ();
cout << "\n";
// problem 5:
multisetUsingMyComparator ();
cout << "\n";
return 0;
}
7
1 Deliverables
Implementation files: Only one file named A5_all.cpp that includes is_palindrome,
test_is_palindrome, second_max, test_second_max,
countStringLambda, countStringFreeFun, countStringFunctor,
charFrequency, multisetUsingMyComparator, as well as all the
supporting functions, functors, and lambdas.
README.txt A text file, as described in the course outline.
2 Marking scheme
80%
Program correctness:
16% per problem
5% Format, clarity, completeness of output
10% Javadoc style documentation before introduction of every class and function, Concise documentation of nontrivial steps in code, choice of variable names, indentation
and readability of program
