如何制作一个while循环但有更多条件C++

Question

cout << "Options:\n1: Change Name\n2: Change Password\n3: Change Address\n4: Withraw\n5: Deposit\nL: Log out\n>";
while (user_input2 != '1' && user_input2 != '2' && user_input2 != '3' && user_input2 != '4' && user_input2 != '5' && user_input2 != 'L')
{
    cout << "Invalid input";
}

So how do I just shortened the while conditions?

I tried doing:

cout << "Options:\n1: Change Name\n2: Change Password\n3: Change Address\n4: Withraw\n5: Deposit\nL: Log out\n>";
while (user_input2 != '1','2','3','4','5','L')
{
    cout << "Invalid input";
}

but it doesn't work.

edit1: "I added more hints to what I wanted to do"

Answer 1

You can use the < and > operators for the range of '1' to '5' , but you'll have to handle the check for 'L' explicitly:

while (user_input2 != 'L' && (user_input2 < '1' || user_input2 > '5'))
{
    cout << "Invalid input";
}

Answer 2

You also can write:

while (user_input2 != '1' && user_input2 != '2' && user_input2 != '3' && user_input2 != 
'4' && user_input2 != '5')
{
    cout << "Invalid input"
}

Answer 3

How about a function where you provide all accepted characters as string?

Demo:

#include <iostream>

bool checkValid(char cChk, std::string_view allowed)
{
  for (char c : allowed) if (cChk == c) return true;
  return false;
}

int main()
{
  char user_input2;
  std::cin >> user_input2;
  if (!checkValid(user_input2, "12345L")) {
    std::cout << "Invalid input\n";
  }
}

Live Demo on coliru

Btw. there is a standard C library function (adopted in C++ standard) which could be used as well:

std::strchr()

It returns a pointer to found character or nullptr and could be used similar like checkValid() in the above sample:

#include <cstring>
#include <iostream>

int main()
{
  char user_input2;
  std::cin >> user_input2;
  if (!std::strchr("12345L", user_input2)) {
    std::cout << "Invalid input\n";
  }
}

Live Demo on coliru

---

Thinking twice (about OPs possible intention), I started to ask why the check is needed at all. Assuming that the valid input has to be processed somehow (I would use a switch for this), invalid input just could be covered as well.

Demo:

#include <iostream>

int main()
{
  for (char user_input2; std::cin >> user_input2;) {
    switch (user_input2) {
      case '1': std::cout << "Change Name\n"; break;
      case '2': std::cout << "Change Password\n"; break;
      case '3': std::cout << "Change Address\n"; break;
      case '4': std::cout << "Withraw\n"; break;
      case '5': std::cout << "Deposit\n"; break;
      case 'l': case 'L': std::cout << "Log out\n"; return 0;
      default: std::cerr << "Invalid input!\n";
    }
  }
}

Input:

12AL

Output:

Change Name
Change Password
Invalid input!
Log out

Live Demo on coliru