Check if a string contains only the characters in another string

问题

I want to write a function that determines if all the letters of an inputted word are contained in another string of acceptable letters.

bool ContainsOnly(std::string inputtedWord, std::string acceptableLetters)
{
    // ... how do I write this?
}

Here's my testing framework:

bool Tester(std::string inputtedWord, std::string acceptableLetters)
{
    if (ContainsOnly(inputtedWord, acceptableLetters)) {
        std::cout << "Good!" << std::endl;
        return true;
    }
    else {
        std::cout << "No good!" << std::endl;
        return false;
    }
}

int main()
{
    std::string acceptableLetters;
    std::string inputtedWord;

    std::cout << "Please input the acceptable letters in your words: " << std::endl;
    std::cin >> acceptableLetters;

    while (inputtedWord != "STOP") 
    {
        std::cout << "Please input the word you would like to test: (type STOP to end testing): " << std::endl;
        std::cin >> inputtedWord;
        Tester(inputtedWord, acceptableLetters);
    }
    return 0;
}

I want the following output:

Please input the acceptable letters in your words: CODING

Please input the word you would like to test: (type STOP to end testing): COIN

Good!

Please input the word you would like to test: (type STOP to end testing): COP

No good!

回答1:

You can use find_first_not_of like this:

bool ContainsOnly(std::string inputtedWord, std::string acceptableLetters)
{
    return inputtedWord.find_first_not_of(acceptableLetters) == std::string::npos;
}

Here's a demo.

回答2:

Put all the acceptable characters to std::set.
Judge if all characters in the strings are in the set via std::all_of.

#include <set>
#include <algorithm>

bool ContainsOnly(std::string inputtedWord, std::string acceptableLetters)
{
     std::set<char> okSet(acceptableLetters.begin(), acceptableLetters.end());
     return std::all_of(inputtedWord.begin(), inputtedWord.end(),
                        [&okSet](char c) 
                        { 
                          return okSet.find(c) != okSet.end(); 
                        });
}

来源：https://stackoverflow.com/questions/64519529/check-if-a-string-contains-only-the-characters-in-another-string

标签

c++

c++11

stdstring