Replace a string to another string using C++ - c++

Question

The problem is I don't know the length of the input string.
My function can only replace if the input string is "yyyy". I think of the solution is that first, we will try to convert the input string back to "yyyy" and using my function to complete the work.
Here's my function:
void findAndReplaceAll(std::string & data, std::string toSearch, std::string replaceStr)
{
// Get the first occurrence
size_t pos = data.find(toSearch);
// Repeat till end is reached
while( pos != std::string::npos)
{
// Replace this occurrence of Sub String
data.replace(pos, toSearch.size(), replaceStr);
// Get the next occurrence from the current position
pos = data.find(toSearch, pos + replaceStr.size());
}
}
My main function
std::string format = "yyyyyyyyyydddd";
findAndReplaceAll(format, "yyyy", "%Y");
findAndReplaceAll(format, "dd", "%d");
My expected output should be :
%Y%d

Answer 1

Use regular expressions.
Example:
#include <iostream>
#include <string>
#include <regex>
int main(){
std::string text = "yyyyyy";
std::string sentence = "This is a yyyyyyyyyyyy.";
std::cout << "Text: " << text << std::endl;
std::cout << "Sentence: " << sentence << std::endl;
// Regex
std::regex y_re("y+"); // this is the regex that matches y yyy or more yyyy
// replacing
std::string r1 = std::regex_replace(text, y_re, "%y"); // using lowercase
std::string r2 = std::regex_replace(sentence, y_re, "%Y"); // using upercase
// showing result
std::cout << "Text replace: " << r1 << std::endl;
std::cout << "Sentence replace: " << r2 << std::endl;
return 0;
}
Output:
Text: yyyyyy
Sentence: This is a yyyyyyyyyyyy.
Text replace: %y
Sentence replace: This is a %Y.
If you want to make it even better you can use:
// Regex
std::regex y_re("[yY]+");
That will match any mix of lowercase and upper case for any amount of 'Y's .
Example output with that Regex:
Sentence: This is a yYyyyYYYYyyy.
Sentence replace: This is a %Y.
This is just a simple example of what you can do with regex, I'd recommend to look at the topic on itself, there is plenty of info her in SO and other sites.
Extra:
If you want to match before replacing to alternate the replacing you can do something like:
// Regex
std::string text = "yyaaaa";
std::cout << "Text: " << text << std::endl;
std::regex y_re("y+"); // this is the regex that matches y yyy or more yyyy
std::string output = "";
std::smatch ymatches;
if (std::regex_search(text, ymatches, y_re)) {
if (ymatches[0].length() == 2 ) {
output = std::regex_replace(text, y_re, "%y");
} else {
output = std::regex_replace(text, y_re, "%Y");
}
}