我需要帮助交换这个字符串

Question

#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