ASCII string combined

Question

I'm working on a program to combine two strings based on the ASCII order of the alphabet and also remove all duplicate letters. So far I have

#include <iostream>
using namespace std;

int main() {
string s1, s2;
string combined;
while (true) {
    cin >> s1 >> s2;
    if (s1 == "quit" && s2 == "quit") break;
    cout << "Read " << "\"" << s1 << "\"" << " and " << "\"" << s2 << "\" -> ";
    combined = s1+s2;
    cout << combined << endl;
}
cout << "Bye";
return 0;
}

the output is supposed to look like Read "binarytriangle" and "ANSIStandard" -> "AINSabdegilnrty" but I can't seem to figure out how to actually combine them based on the order of the alphabet and remove the duplicate letters. Online I only found how to get the numerical value of a char based on the ASCII order and not ordering the two strings. I'm thinking of using a for loop, but I'm not sure what I should put inside the parenthesis.

[`std::operator+(std::basic_string)`](https://en.cppreference.com/w/cpp/string/basic_string/operator%2B); [`std::sort`](https://en.cppreference.com/w/cpp/algorithm/sort); [`std::unique`](https://en.cppreference.com/w/cpp/algorithm/unique); [`std::string::erase`](https://en.cppreference.com/w/cpp/string/basic_string/erase). — molbdnilo, Mar 28 '19 at 15:41
To elaborate a bit on the comment by @molbdnilo, which gives you the names of the appropriate standard library functions -- first sort the characters, then remove the duplicates. — Pete Becker, Mar 28 '19 at 16:03

score 0 · Answer 1 · answered Mar 28 '19 at 16:08

This covers what @molbdnilo wrote in a comment but with inline comments in the code. This part:

while (true) {
    cin >> s1 >> s2;

is a potential pitfall. If the writing side closes the stream, you'll end up with an endless loop. Also, using namespace std; is a bad practice.

#include <iostream>
#include <algorithm> // std::sort

// Dont do this:
// using namespace std;

int main() {
    std::string s1, s2;
    std::string combined;

    // check if  std::cin  is true in a boolean context after having tried to extract
    // the strings. If it's not true, you'll may end up with an endless loop (if
    // the writing side closed the stream).
    while(std::cin >> s1 >> s2) {
        if(s1 == "quit" && s2 == "quit") break;
        std::cout << "Read "
                  << "\"" << s1 << "\""
                  << " and "
                  << "\"" << s2 << "\" -> ";
        combined = s1 + s2;

        // sort the chars in the string.
        std::sort(combined.begin(), combined.end());

        // move repeated chars to the end of the string and return an iterator to
        // what will become the new end of the string
        std::string::iterator new_end = std::unique(combined.begin(), combined.end());
        // the string is just as long as before here, but all the repeated chars
        // are at the end, so,

        // erase all chars from new_end to current end()
        combined.erase(new_end, combined.end());

        std::cout << combined << "\n"; // std::endl for flushing is unncessary in most cases
    }
    std::cout << "Bye\n";
}

ASCII string combined

1 Answers1