lrecursion.c

#include<stdio.h>
#include<string.h>

// Program in C to remove left recursion from given grammar
// Removing Left Recursion

/*Input: A->Axy|z
Output: A->zA'
        A'->xyA'|e
*/

int main()
{
    int i,j,n,k;
    int lrec = 0;
    char prod[100];
    char newprod1[100]= "";
    char newprod2[100]= "";

    char alpha[100] = "";
    char beta[100]= "";
    char sts[20]="";
    scanf("%s",prod);
    sts[0] = prod[0];   // sts is Start Symbol
    int size = (int)(strlen(prod));
    
    for(i=0;i<size;i++)
    {
        if(prod[i] == '|')
        {
            k = i;
        }
    }
    if(prod[3] == prod[0])
    {
        lrec = 1;
    }
    if(lrec == 1)
    {   
        int c =0;
        k = k-1;
        for(i=4;i<=k;i++)
        {
            alpha[c] = prod[i];
            c++;
        }
        c = 0;
        for(i=k+2;i<size;i++)
        {
            beta[c] = prod[i];
            c++;
        }

        strcat(newprod1,sts);
        strcat(newprod1,"->");
        strcat(newprod1,beta);
        strcat(newprod1,sts);
        strcat(newprod1,"'");

        strcat(newprod2,sts);
        strcat(newprod2,"'");
        strcat(newprod2,"->");
        strcat(newprod2,alpha);
        strcat(newprod2,sts);
        strcat(newprod2,"'");
        strcat(newprod2,"|e");

        printf("\n%s\n%s",newprod1,newprod2);
    }
}