Insert character infront of each word in a string using C++ - c++

Question

I have a string, for example; "llama,goat,cow" and I just need to put a '#' in front of each word so my string will look like "#llama,#goat,#cow", but I need the values to be dynamic also, and always with a '#' at the beginning.
Not knowing a great deal of C++ could someone please help me find the easiest solution to this problem? Many thanks in advance.

Answer 1

For the moment, I'm going to assume that the words are always separated by commas. If that's correct, something like this should at least be fairly close:
// warning: untested.
std::string input("llama,goat,cow");
std::ostringstream o;
std::string word;
std::istringstream i(input);
while (std::getline(input, word, ','))
o << "#" << word << ",";
std::string result(o.str(), o.str().size()-1);
// show the result:
std::cout << result;
Edit: there are two different functions named getline: one is a member of an iostream, and reads the input data into a "raw" array of char. The other is a global free function that reads the input data into a std::string. This is the one you want. To get it declared, you have to #include <string>.

Answer 2

Here's a C++-style way:
Use the basic_string class in the standard library:
basic_string
('string' is an alias for basic_string)
You can use find_first_of() to find the first character that matches one of your wordbreak delimiters. You can then use the append operator (+=) to append the segments of the string to a new string, and then append '#' symbols in between.
Here's a C-style way:
You could start with strtok_s
Which will "tokenize" the string by searching for word-break delimiters like commas or spaces. You'll then be able to copy the parts between the delimiters into another buffer and then put the '#' symbols between them as you go along
For that, I'd use strcpy_s to copy piece-by-piece into a new buffer.

Answer 3

Judging by insertable's comments, (s?) he's trying to get this code working... So let me offer my take...
As with the others, I'm presuming each word is delimited by a single ",". If you can have multiple character delimiters, you'll need to add a second find (i.e. find_first_not_of) to find the start/end of each word.
And yes, you could insert the '#' characters into the preexisting string. But inserting for each word gets a little inefficient (O(N^2)) unless you're clever. That sort of cleverness usually comes with a high maintenance/debugging cost. So I'll just stick to using two strings...
(There ought to be some brilliant way to do this with STL algorithms. But I'm sick and I just don't see how to accommodate insertion right now...)
References: C++-strings C++-strings STL count_if
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
#define SHOW(X) cout << # X " = " << (X) << endl
int main()
{
// 0123456789_123456789_1234
string inString(",llama,goat,cow,,dog,cat");
string outString;
/* This code assumes inString.size() > 0 */
const iterator_traits<string::iterator>::difference_type numberOfWords
= count_if( inString.begin(), inString.end(),
bind2nd( equal_to<char>(), ',' ) )
+ 1;
string::size_type startIndex, endIndex;
outString.reserve( inString.length() + numberOfWords );
for ( startIndex = endIndex = 0;
endIndex != string::npos;
startIndex = endIndex + 1 )
{
outString += "#";
/* No startIndex+1 here. We set startIndex=endIndex+1 in the for loop */
endIndex = inString . find_first_of( ",", startIndex );
outString . append ( inString, startIndex,
( (endIndex == string::npos)
? string::npos : endIndex - startIndex + 1) );
}
SHOW( numberOfWords );
SHOW( inString );
SHOW( outString );
SHOW( inString.size() );
SHOW( outString.size() );
SHOW( inString.capacity() );
SHOW( outString.capacity() );
}