Program to check whether a grammar is left Recursion and remove left Recursion of grammar

Left recursion :

#include<iostream.h>

#include<stdio.h>

#include<conio.h>

#include<string.h>

struct production

{

            char l;

            char r[10];

            int rear;

};

struct production prod[20],pr_new[20];        

int p=0,b=0,d,f,q,n,flag=0;

char terminal[20],nonterm[20],alpha[10];

char x,epsilon='^';

void main()

{

    clrscr();

       cout<<"Enter the number of terminals: ";

    cin>>d;

    cout<<"Enter the terminal symbols for your production: ";

    for(int k=0;k<d;k++)

    {

      cin>>terminal[k];

    }

  

    cout<<"\nEnter the number of non-terminals: ";

    cin>>f;

    cout<<"Enter the non-terminal symbols for your production: ";

    for(k=0;k<f;k++)

    {

      cin>>nonterm[k];

    }

 

    cout<<"\nEnter the number of Special characters(except non-terminals): ";

    cin>>q;

    cout<<"Enter the special characters for your production: ";

    for(k=0;k<q;k++)

    {

      cin>>alpha[k];

    }

  

    cout<<"\nEnter the number of productions: ";

    cin>>n;

    for(k=0;k<=n-1;k++)

    {

      cout<<"Enter the "<< k+1<<" production: ";

      cin>>prod[k].l;

      cout<<"->";

      cin>>prod[k].r;

      prod[k].rear=strlen(prod[k].r);

    }

 

    for(int m=0;m<f;m++)

    {

      x=nonterm[m];

      for(int j=0;j<n;j++)

      {

               if((prod[j].l==x)&&(prod[j].r[0]==prod[j].l))

                  flag=1;

      }

      for(int i=0;i<n;i++)

      {

               if((prod[i].l==x)&&(prod[i].r[0]!=x)&&(flag==1))

               {

                           pr_new[b].l=x;

                           for(int c=0;c<prod[i].rear;c++)

                           pr_new[b].r[c]=prod[i].r[c];

                           pr_new[b++].r[c]=alpha[p];

               }

               else if((prod[i].l==x)&&(prod[i].r[0]==x)&&(flag==1))

               {

                          pr_new[b].l=alpha[p];

                          for(int a=0;a<=prod[i].rear-2;a++)

                           pr_new[b].r[a]=prod[i].r[a+1];

                          pr_new[b++].r[a]=alpha[p];

                          pr_new[b].l=alpha[p];

                          pr_new[b++].r[0]=epsilon;

                }

                else if((prod[i].l==x)&&(prod[i].r[0]!=x)&&(flag==0))

                {

                           pr_new[b].l=prod[i].l;

                           strcpy(pr_new[b].r,prod[i].r);

                           b++;

                }

            }

            flag=0;

            p++;

  }

 

    cout<<"\n\n*******************************************";

    cout<<"\n       AFTER REMOVING LEFT RECURSION       ";

    cout<<"\n*******************************************"<<endl;

    for(int s=0;s<=b-1;s++)

            {

                        cout<<"Production "<<s+1<<" is: ";

                        cout<<pr_new[s].l;

                        cout<<"->";

                        cout<<pr_new[s].r;

                        cout<<endl;

            }

    getche();

}