Re: Stroustrup 5.9 exercise 12
"arnuld" <geek.arnuld@gmail.com> wrote:
On Apr 10, 1:45 pm, "Erik Wikstr?m" <eri...@student.chalmers.se> wrote:
You'll want to compare parts of the string, starting with the two
first characters, then the second and third characters and so on. Be
mindful of the fact that you compare with two characters so that you
don't try to compare with the last and the one after the last. So what
you want to do is loop over all the characters from the first to the
second to last.
In the string-case you can use the substr() method to get a part of a
string, or you can use []/at() to get individual characters, the
advantage of using []/at() is that the string and C-string
implementations will be quite similar.
i will use "substr()". see down here for my dirty implementation:
It might be easier to require that you search for a pair of letters
and later, if you still want to, generalize it to work with single
characters or more than a pair.
i ahve tried to make it modifiable. i am sure folks here will have
lots of advice for improving my code as it does not look like
Standard C++ code to me :-(
Your code is fine, but doing more work than it needs to. It can be
simplified quite a bit. I.E., the only problem I see is that you don't
yet know what the standard library already has available.
-------- PROGRAMME ---------
/* Strouostrup, 5.9, exercise 12
*
*
* STATEMENT:
* write a function that counts the number of occurrences of a pair of
* letters ina "string" and another that does the same in a zero-
terminated
* array fo char(a C style string). e.g. the pair "ab" appears twice in
* "xabaacbaxabb"
*
*/
#include<iostream>
#include<string>
int main()
{
std::string s, pair;
std::cout << "Enter a word: ";
std::cin >> s;
std::cout << "Enter a pair of letters or a single letter you want to
find in the word: ";
std::cin >> pair;
const int ps = pair.size();
const int ss = s.size();
int matches = 0;
if(ps < ss)
{
for(int i=0; i < ss; ++i)
if(pair == s.substr(i,ps))
++matches;
}
Look up std::string::find...
http://www.dinkumware.com/manuals/?manual=compleat&page=string2.html#basi
c_string::find
std::cout << "you entered: \t"
<< s
<< '\n'
<< "letter(s) to match: "
<< pair
<< '\n'
<< "Matches are: "
<< matches
<< std::endl;
return 0;
}
One last comment. It's time to start putting code into separate
functions:
int countOccurrences( const std::string& source, const std::string& pair
)
{
// do the job here
// return the result
}
int main()
{
// get the data
// call 'countOccurrences' using the data
// put the results
}