Question

Using c++, write a program that reads a sequence of characters from the keyboard (one at a
time) and creates a string including the distinct characters entered and displays the
string on the screen. The input terminates once the user enters a white-space
character or the user has entered 50 distinct characters.

Do not use C-Strings.
2. Use the following function to append character “ch” to the string “s”:
s.push_back(ch);
3. Read the input characters one by one, i.e. do not read the input as a string.
4. Do not use arrays.

Answer 1

The required C++ code is as follows:----

#include<bits/stdc++.h>
using namespace std;
int main(void)
{
        string s; //  String to store the characters 
        s="";
        
        char ch;
        
        
        while(s.length()!=50) // Checking whether the length of string is 50 or not
        {                                     
                cout<<"Enter a character"<<endl; // Prompt the user to enter the next character
                cin>>ch;
                
                if(isspace(ch)) // isspace (char ch) is a function in C which checks if the character passed as an argument is a whitespace character or not
                break; // Break out of loop if character entered is a whitespace character...
                
                bool found=false; // variable to check if the recently entered character is a distinct character or not
                for (int i=0;i<s.length();i++) // Loop to check if the recently entered character is already present in the string or not
                {
                        if(s[i]==ch)
                        found=true;
                }
                 
                if(!found) // If the character is distinct we append it to the string...automatically length of string increases by 1..
                s.push_back(ch); // We push the recently entered distinct character at the end of the string..
                
        }
        
        if(s.length())
        cout<<"The resultant string is --- "<<s<<endl;
        else
        cout<<"The resultant string is an empty string"<<endl; // Case when the first character entered by the user is a whitespace character
}