c++ Find and replace whole word - c++

Question

How i can Find and replace (Match Whole word).
I have this.
void ReplaceString(std::string &subject, const std::string& search, const std::string& replace)
{
size_t pos = 0;
while ((pos = subject.find(search, pos)) != std::string::npos) {
subject.replace(pos, search.length(), replace);
pos += replace.length();
}
}
but it dosnt search for whole word.
for example if i try
string test = "i like cake";
ReplaceString(test, "cak", "notcake");
it will still replace but i want it to match whole word.

Answer 1

You're just blindly replacing any instances of search with replace without checking if they're full words prior to performing the replacement.
Here are just a couple of things you can try to work around that:
Split the string into individual words, then check each word against search, and replace if necessary. Then rebuild the string.
Replace only if pos-1 and pos + search.length() + 1 are both spaces.

Answer 2

Regular expressions solution if you have access to c++11 compiler:
#include <iostream>
#include <string>
#include <regex>
void ReplaceString(std::string &subject, const std::string& search, const std::string& replace)
{
// Regular expression to match words beginning with 'search'
std::regex e ("(\\b("+search+"))([^,. ]*)");
subject = std::regex_replace(subject,e,replace) ;
}
int main ()
{
// String to search within and do replacement
std::string s ("Cakemoney, cak, cake, thecakeisalie, cake.\n");
// String you want to find and replace
std::string find ("cak") ;
// String you want to replace with
std::string replace("notcake") ;
ReplaceString(s, find, replace) ;
std::cout << s << std::endl;
return 0 ;
}
Output:
Cakemoney, notcake, notcake, thecakeisalie, notcake.
More about the regular expression string (\\b("+search+"))([^,. ]*). Note that after replacing search this string will be:
(\\b(cak))([^,. ]*)
\b(cak) - match words beginning with cak regardless of what comes after
([^,. ]*) - matches anything up to a ,, ., or (space).
The above basically just rips off the example provided here. The answer is case sensitive, and will also replace punctuation other than the three listed after ^, but feel free to learn more about regular expressions to make a more general solution.