Question

I need to write a C++ program that appends "not" into the string without using the append method or any standard libraries. It should return the string if there isn't an "is" in it.

Examples:

is is = is not is not

This is me = This is not me

What is yellow? = What is not yellow?

The sky is pink = The sky is not pink

isis = isis

What happened to you? = What happened to you?

Answer 1

C++ Code :

#include<iostream>
using namespace std;

// this method appends "not" into the string without using the append method or any standard libraries.
// this method returns the string if there isn't an "is" in it.
// this method accepts a parameter of user input string
string solve(string s)
{
   string res = "";           // this is the resultant string
   int n = (int)s.size();               // getting the size of the input string
  
   // if the size of the input string is 1, then directly return it
   if(n==1)          
       return s;
      
   // if the size of the input string is 2, then check whether it is "is" or not
   else if(n==2)
   {
       // if the input string is "is", then simply add "is not" to the resultant string and return it
       if(s[0]=='i' && s[1]=='s')
       {
           res += "is not";
           return res;
       }
      
       // if the input string is not "is", then simply return it directly
       else
           return s;
   }
  
   // if the size of the input string is greater than 2
   else
   {
       for(int i=0;i<n;i++)
       {
           // this is for first index of the input string
           if(i==0)
           {
               // if the first word of the input string is "is"
               if(s[i]=='i' && s[i+1]=='s' && s[i+2]==' ')
               {
                   res += "is not";
                   i++;
               }
              
               // else simply add the current character to the resultant string
               else
                   res += s[i];
           }
          
           // this is for (n-2)th index of the input string
           else if(i==n-2)
           {
               // checking if the last word of the input string is "is"
               if(s[i-1]==' ' && s[i]=='i' && s[i+1]=='s')
               {
                   res += "is not";
                   i++;
               }
              
               // else simply add the current character to the resultant string
               else
                   res += s[i];
           }
          
           // this is for rest of the character of the input string
           else
           {
               // if the current index word is "is", then simply add "is not" to the resultant string
               if(s[i-1] == ' ' && s[i]=='i' && s[i+1]=='s' && s[i+2]==' ')
               {
                   res += "is not";
                   i+=2;
               }
              
               // else simply add the current character to the resultant string
               res += s[i];
           }
       }
      
       // returning the resultant string from this method
       return res;
   }
}

int main()
{
   string s;           // this variable will take user input of string
   cout<<"Enter a string : ";               // asking for the user input of string
   getline(cin,s);                   // taking input from the user
  
   string result = solve(s);               // calling solve() for getting the resultant string or expected output and storing to the result variable
  
   cout<<"Resultant string is : "<<result<<"\n";               // printing the resultant string
}

Output :