I need help swapping this string [closed] - c++

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#include <iostream>
using namespace std;
int main()
{
string sentence;
string output;
string product1;
string product2;
char pr1;
string product;
int i;
getline (cin,sentence);
char pr2;
cin >> pr1;
cin >> pr2;
for (i=0; i < sentence.length();i++){
pr1 = sentence[i]; //asdfg---> g
pr2 = sentence[0]; //--> a
}
output += pr1+sentence+pr2;
cout << output;
return 0;
}
This code is made to swap letters, but for example when I enter asdfg I get gaasdfga. When I enter that, I want to swap g and a. Any idea what I should do? Any idea what's wrong, and how I can improve it?

Answer 1

The below assigns new values to pr1 and pr2. The characters you entered will be lost.
pr1 = sentence[i]; //asdfg---> g
pr2 = sentence[0]; //--> a
To swap the first found of each of the two entered characters, use std::string::find and then std::swap
Example:
#include <utility>
#include <string>
#include <iostream>
int main() {
std::string sentence = "asdfg";
char pr1 = 'g';
char pr2 = 'a';
auto pos1 = sentence.find(pr1);
auto pos2 = sentence.find(pr2);
if(pos1 != sentence.npos && pos2 != sentence.npos) {
std::swap(sentence[pos1], sentence[pos2]);
}
std::cout << sentence << '\n';
}
Output:
gsdfa
An alternative to std::swap(sentence[pos1], sentence[pos2]); would be to do the swap manually:
char temp = sentence[pos1];
sentence[pos1] = sentence[pos2];
sentence[pos2] = temp;
or via a user defined swapper function that you call just like you'd call std::swap:
template<class T>
void swapper(T& lhs, T& rhs) {
// move construct a temporary variable from the argument on the
// left hand side
T temp = std::move(lhs);
// move assign the left hand side from the right hand side
lhs = std::move(rhs);
// move assign the right hand side from the temporary variable
rhs = std::move(temp);
}