changing case for first and last letter C++ - c++

Question

i need ThE FirsT AnD LasT letter of every word to be uppercase and the rest lowercase but function convertFirstAndLastLetter only does the first and last of the sentence.
void convertFirstAndLastLetter(char wrd[])
{
size_t last = strlen(wrd) - 1;
size_t first = 0;
wrd[first] = toupper(wrd[first]);
wrd[last] = toupper(wrd[last]);
for(int i = first + 1 ; i < last - 1; i++)
{
wrd[i] = tolower(wrd[i]);
}
}
int main ()
{
float val;
cout << "ent ";
cin >> val;
if (val == 4)
{
char wrd[256];
cin.ignore();
cin.getline(wrd,256);
convertFirstAndLastLetter(wrd);
cout << wrd;
return 0;
}
}

Answer 1

Right now you're passing a whole line to your function, so the first and last characters are all that is being changed.
To fix that you need to split the line up into words which could be done by reading a word at a time using std::cin >> word, or reading the whole line and then using a std::stringstream to split it up. Both are about the same, but I used a stringstream.
Next, if I'm reading your statement correctly, you want to have the first and last "letter" of each word uppercase and the rest lowercase. That means we need to find the first and last letter in case there is punctuation before or after the word.
Once the first and last are determined it's easy to uppercase them and lowercase the rest.
#include <iostream>
#include <string>
#include <sstream>
#include <cctype>
void convertFirstAndLastLetter(std::string& word)
{
if(!word.empty())
{
size_t first = 0;
size_t last = word.size() - 1;
//Find first alpha character
while(first < word.size() && !std::isalpha(word[first]))
{
++first;
}
//If the position is valid, uppercase it
if(first < word.size())
{
word[first] = static_cast<char>(std::toupper(word[first]));
}
//Find last alpha character
while(last > first && !std::isalpha(word[last]))
{
--last;
}
//If the position is valid, uppercase it
if(last > first)
{
word[last] = static_cast<char>(std::toupper(word[last]));
}
for(size_t i = first + 1; i < word.size() && i < last; ++i)
{
if(std::isalpha(word[i]))
{
word[i] = static_cast<char>(std::tolower(word[i]));
}
}
}
}
int main()
{
float val;
std::cout << "ent ";
std::cin >> val;
std::cin.ignore();
if(val == 4)
{
std::string line;
if(std::getline(std::cin, line))
{
std::string word;
std::stringstream ss(line);
while(ss >> word)
{
convertFirstAndLastLetter(word);
std::cout << word << " ";
}
std::cout << "\n";
}
}
return 0;
}
Keep in mind this will discard any extra spaces at the beginning and end of each line as well as any extra spaces between words. The way I am printing them out will also add an extra space at the end of each line. You didn't mention any concern about those things in your question, so I didn't worry about them. They are all solvable with a little extra effort.

Answer 2

Now with less duplicated code:
#include <algorithm>
#include <iostream>
#include <string>
template<typename It>
void upperFirstAlpha(It begin, It end)
{
auto first = std::find_if(begin, end, isalpha);
if (first != end)
*first = toupper(*first);
}
int main()
{
for (std::string s; std::cin >> s;) {
std::transform(s.begin(), s.end(), s.begin(), tolower);
upperFirstAlpha(s.begin(), s.end());
upperFirstAlpha(s.rbegin(), s.rend());
std::cout << s << ' ';
}
}
As #Retired Ninja pointed out the first version wouldn't work for punctuation, whether this version is what you are looking for depends on what your input looks like.

Answer 3

This function
void convertFirstAndLastLetter(char wrd[])
{
size_t last = strlen(wrd) - 1;
size_t first = 0;
wrd[first] = toupper(wrd[first]);
wrd[last] = toupper(wrd[last]);
for(int i = first + 1 ; i < last - 1; i++)
{
wrd[i] = tolower(wrd[i]);
}
}
is wrong. For example if character array is empty that is it has only the terminating zero then expression strlen(wrd) - 1 will give you the maximum value for an object of type size_t and in the next statement
wrd[last] = toupper(wrd[last]);
you will try to change memory beyond the array.
Also if you use standard function strlen then you have to include header <cstring>.
In fact there is no any need to use function strlen. The code can be written simpler
#include <cctype>
//...
void convertFirstAndLastLetter( char wrd[] )
{
if ( *wrd )
{
*wrd = std::toupper( *wrd );
if ( *++wrd )
{
while ( *( wrd + 1 ) )
{
*wrd = std::tolower( *wrd );
++wrd;
}
*wrd = std::toupper( *wrd );
}
}
}

Answer 4

#include "stdafx.h"
#include <string>
#include <iostream>
using namespace std;
void convertFirstAndLastLetter(char wrd[])
{
size_t last = strlen(wrd) - 1;
size_t first = 0;
wrd[first] = toupper(wrd[first]);
wrd[last] = toupper(wrd[last]);
for(int i = first + 1 ; i < last; i++)
{
wrd[i] = tolower(wrd[i]);
}
}
int _tmain(int argc, _TCHAR* argv[])
{
float val;
cout << "ent ";
cin >> val;
if (val == 4)
{
char wrd[256];
cin.ignore();
cin.getline(wrd,256);
convertFirstAndLastLetter(wrd);
cout << wrd;
return 0;
}
}