How to find all the numbers in a string and form a new one from them?

Question

C++ / C#

Task: A
character string is entered from the keyboard. You need to find all the numbers and form a new string from them.
I understand how this can be done through a char array. But is it possible to somehow implement it through string? If so, how?

Answer 1

Need a sort function

No.

#include<iostream>
#include<string>
#include<algorithm>
using namespace std;

int main()
{
  string src;
  getline(cin, src);

  string dst;
  copy_if(src.begin(), src.end(), back_inserter(dst), ::isdigit);

  cout << dst;
}