expression evaluation.cpp

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

typedef struct  node
 { int power;
   float coeff;
   struct node *next;
 }node;

      node *  insert(node *head,int power1,float coeff1);
      node *  create();
      node *  padd(node *p1,node *p2);
      node *  pmul(node *p1,node *p2);
      float eval(node *p1,float x);
      void print(node *head);


node *insert(node *head,int power1,float coeff1)
      {  node *p,*q;
     /*terms are store in increasing order of power*/
     /*pointer is used to locate the correct place of insertion.
       pointer p is used to store the address of the node created for
       the current term.If a term with same power is found,coefficients
       are added*/
       p=(node*) malloc(sizeof(node));
       p->power=power1;
       p->coeff=coeff1;
       p->next=NULL;
       if(head==NULL)
     {
          head=p;
          head->next=head;
          return(head);
     }
       if(power1>head->power)
      {
          p->next=head->next;
          head->next=p;
          head=p;
          return(head);
      }
       if(power1==head->power)
      {
          head->coeff=head->coeff+coeff1;
          return(head);
      }

     q=head;
     while(q->next!=head && power1>=q->next->power)
           q=q->next;
     if(p->power==q->power)
           q->coeff=q->coeff+coeff1;
     else
       {
           p->next=q->next;
           q->next=p;
       }
    return(head);
  }


 node *create()
   {
       int n,i,power1;
       float coeff1;
       node *head=NULL;
       printf("\nEnter No. of Terms:");
       scanf("%d",&n);
       printf("\nenter a term as a tuple of (power,coefficient) : ");
       for(i=1;i<=n;i++)
     {   scanf("%d%f",&power1,&coeff1);
         head=insert(head,power1,coeff1);
     }
       return(head);
  }

 node * padd(node *p1,node *p2)
 {   node *p;
     node *head=NULL;
     int power;float coeff;
     p=p1->next;
     do
     {
         head=insert(head,p->power,p->coeff);
         p=p->next;
     } while(p!=p1->next);
     p=p2->next;
     do
     {
         head=insert(head,p->power,p->coeff);
         p=p->next;
     } while(p!=p2->next);
     return(head);
  }

 node *pmul(node *p1,node *p2)
 {   node *head1,*head2;
     node *head=NULL;
     head2=p2->next;
      do
       {  head1=p1->next;
      do
        {
 //    for(p=head1;p!=NULL;p=p->next)
         head=insert(head,head1->power+head2->power,head1->coeff * head2->coeff);
         head1=head1->next;
       }while(head1!=p1->next);
    head2=head2->next;
       }while(head2!=p2->next);
     return(head);
 }

 float eval(node *head,float x)
 {  float value=0.00;
    node *p;
    p=head->next;
    do
       {  value=value+p->coeff * pow(x,p->power);
      p=p->next;
       }while(p!=head->next);
    return(value);
 }

 void print( node *head)
 {  node *p;
    p=head->next;
    printf("\n");
    do
     {
    printf("%6.2fx^%d   ",p->coeff,p->power);
    p=p->next;
     }while(p!=head->next);
 }


 void main()
 { node *p1,*p2,*p3;
   int op;
   float value,x;
   p1=p2=p3=NULL;
//  clrscr();
   do
     { printf("\n1)Create first polynomial");
       printf("\n2)Create second polynomial");
       printf("\n3)Print first polynomial");
       printf("\n4)Print second polynomial");
       printf("\n5)Add\n6)Multiply\n7)Evaluate First Polynomial\n8)Quit");
       printf("\nEnter Your Choice: ");
       scanf("%d",&op);
       switch(op)
    { case 1: p1=create();break;
      case 2: p2=create();break;
      case 3: print(p1);break;
      case 4: print(p2);break;
      case 5: p3=padd(p1,p2);
          print(p3);break;
      case 6: p3=pmul(p1,p2);
          print(p3);break;
      case 7: printf("\nEnter the value of X:");
          scanf("%f",&x);
          value=eval(p1,x);
          printf("\nEvaluated value = %6.2f",value);
          break;
      }
       }while(op!=8);
 }