Is there a way to erase two given values with loop? - c++

Question

How do I erase if string sdl1 holds two values like "37". Considering that are two different values 3 and 7. Do I need some sort of list or only loop? Thank you
#include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <conio.h>
#include <sstream>
#include <stdio.h>
#include <iterator>
using namespace std;
void eraseAllSubStr(std::string & mainStr, const std::string & toErase)
{
size_t pos = std::string::npos;
while ((pos = mainStr.find(toErase)) != std::string::npos)
{
mainStr.erase(pos, toErase.length());
}
}
int main()
{
std::string str = "123456789";
//Let's Say I want to delete 5 and 8 and string sdl1 = "58".
string sdl1 = "5";
eraseAllSubStr(str, sdl1);
std::cout << str << std::endl;
return 0;
}
The output of the minimal reprod. example:
12346789
5 was erased.
But I would like to erase two values like 5 and 8 where string sdl1 = "58"

Answer 1

If I understand your actual question:
"What If I want to remove "58" like 5 and 8?"
and you want to provide std::string sdl1 = "58"; and have both 5 and 8 removed from std::string str = "123456789"; in a single loop, then you can simply use std::basic_string::find_first_of to locate the position of either 5 or 8 and then use std::basic_string::erase to remove the character. The only constraint is you only want to attempt the removal of characters while str.find_first_of (sdl1) != std::basic::npos).
A for loop is tailor made for the implementation, e.g.:
std::string str = "123456789";
//Let's Say I want to delete 5 and 8 and string sdl1 = "58".
std::string sdl1 = "58";
for (size_t pos = str.find_first_of (sdl1);
pos != std::string::npos;
pos = str.find_first_of (sdl1))
str.erase (pos, 1);
Putting it altogether in a short example, you could do:
#include <iostream>
#include <string>
int main (void) {
std::string str = "123456789";
//Let's Say I want to delete 5 and 8 and string sdl1 = "58".
std::string sdl1 = "58";
for (size_t pos = str.find_first_of (sdl1);
pos != std::string::npos;
pos = str.find_first_of (sdl1))
str.erase (pos, 1);
std::cout << "str: " << str << '\n';
}
Example Use/Output
$ ./bin/erasechars
str: 1234679

Answer 2

Erase as substring
If you want to erase as a substring, the code you wrote is solution to your problem. Run again your code by putting
std::string str = "123456789";
string sdl1 = "56";
You will get your ouput 1234789.
Once again set the inputs
std::string str = "12345678956123";
string sdl1 = "56";
You will get your output 1234789123
So you've successfully removed all the occurrences of 56 from your main string str.
The way std::string::find() works, it searches the string for the first occurrence of the sequence specified by its arguments. So it will work same for a substring as it works for a single character.
Similarly std::string::erase() erases a part of the string, reducing its length. All you need is to specify the starting index and the length of the substring (i.e. string ::erase (size_type idx, size_type len )) you would like to remove.
So, your code will work for removing all the occurrences of a given substring.
Erase as character
If you want to remove one or more characters from a string like you mentioned 5 and 8. You can use your code with simple modification to your eraseAllSubStr function.
void eraseAllSubStr(std::string & mainStr, const std::string & toErase)
{
size_t pos = std::string::npos;
// erase all the occurrences of the characters that are
// given through toErase string
// and obviously the length of a char is 1
for( int id = 0; id < toErase.size(); id++)
{
while ((pos = mainStr.find(toErase[id])) != std::string::npos)
{
mainStr.erase(pos,1);
}
}
}