Question

How to write a C++ program that lets the user enter a string and checks if it is an accepted polynomial. Accepted polynomials need to have one term per degree, no parentheses, spaces ignored.

Answer 1

#include <iostream>
#include<cctype>
#include<algorithm>
using namespace std;
int main()
{
   string s;
   getline(cin,s);
   s.erase(remove(s.begin(),s.end(),' '),s.end());
   int d;
   int flag=0;
   if(s.length()>=4)
     { d=s[3];
       if(!isdigit(d))
       {
         flag=1;
       }
     }
   for(int i=0;i<s.length();i++)
   {
      if(s[i]=='('|| s[i]==')')
      {
          flag=1;
          break;
      }
      else if(s[i]==' ')
        continue;
     else if(isdigit(s[i]) && (i+4)<s.length())
      {
         if(s[i+1]=='x')
         {  
             if(s[i+2]=='^')
              {
                  if(isdigit(s[i+3]))
                  {   
                      if(d==s[i+3])
                     {
                         d--;
                      if(s[i+4]=='+' || s[i+4]=='-')
                      {
                          i+=4;
                      }
                      else
                      {
                          flag=1;
               
                          break;
                      }
                      
                     }
                     else
                     {
                         flag=1;
                    
                         break;
                     }
                  }
                  else
                  {
                      flag=1;
                     
                      break;
                  }
              }
              else
              {
                  flag=1;
                
                  break;
              }
         }
         else
         {
             flag=1;
           
             break;
         }
      }
      else if(i==s.length()-1)
        {
            if(!isdigit(s[i]))
            {
                flag=1;
               
                break;
            }
        }
      else
      {
          flag=1;
          
          break;
      }
   }
   if(flag==1 || !isdigit(s[s.length()-1]))
    cout<<"Not Accepted";
   else
    cout<<"Accepted";
   return 0;
}

OUTPUT:

NOTE:

STRING SHOULD BE OF FORMAT LIKE ax^3+bx^2+cx^1+d

where a,b,c,d are numeric values.