Write A Program For Representation of sparse matrices

Program

Here is a program for the addition of two sparse matrices:

# include <stdio.h>
# include <stdlib.h>
struct snode
   {
      int row,col,val;
      struct snode *link;
   };

struct snode *insert(struct snode *, int,int,int);
void printlist ( struct snode * );
struct snode *sadd(struct snode *, struct snode *);
//struct pnode *sortlist(struct pnode *);

struct snode *insert(struct snode *p, int r,int c,int val)
{
   struct snode *temp;
   if(p==NULL)
   {
      p=(struct snode *)malloc(sizeof(struct snode));
      if(p==NULL)
      {
   printf("Error\n");
          exit(0);
      }
      p->row = r;
      p->col = c;
      p->val = val;
      p-> link = NULL;
   }
   else
   {
      temp = p;
      while (temp-> link!= NULL)
     temp = temp-> link;
      temp-> link = (struct snode *)malloc(sizeof(struct snode));
      if(temp -> link == NULL)
      {
   printf("Error\n");
          exit(0);
      }
     temp = temp-> link;
      temp-> row = r;
      temp->col= c;
      temp->val=val;
      temp-> link = NULL;
   }
   return (p);
}

/* A function to add two sparse matrices */
struct snode *sadd(struct snode *p, struct snode *q)
{
   struct snode *r = NULL;
   int val;
   while((p!=NULL) && (q != NULL))
            {
               if(p->row < q->row)
               {
                  r = insert(r,p->row,p->col,p->val);
                  p = p->link;
               }
             else
                if(p->row > q->row)
                {
                  r = insert(r,q->row,q->col,q->val);
                  q = q->link;
                }
             else
   if( p->col < q->col)
                {
      r = insert(r,p->row,p->col,p->val);
                  p = p->link;
                }
   else
            if(p->col > q->col)
               {
                  r = insert(r,q->row,q->col,q->val);
                  q = q->link;
               }
             else
             {
               val = p->val + q->val;
               r = insert( r, p->row,p->col,val);
               p = p->link;
               q = q->link;
             }
     }
   while(p != NULL)
            {
                  r = insert( r, p->row ,p->col,p->val);
                  p = p->link;
            }
            while(q!=NULL)
            {
                  r = insert( r, q->row ,q->col,q->val);
                  q = q->link;
            }
   return(r);
   }

   void printlist ( struct snode *p )
   {
      printf("The resultant sparse matrix is\n");
      while (p!= NULL)
           {
      printf("%d %d % d\n",p-> row,p->col,p->val);
               p = p-> link;
        }
   }
   void main()
   {
      int r,n,c,val;
      struct snode *s1 = NULL ;
      struct snode *s2=NULL;
      struct snode *result = NULL;
      printf("Enter the number of non-zero terms in the sparse matrix1 \n");
      scanf("%d",&n);
      printf("Enter the terms in the sparse matrix1 in the increasing
order of row indices and for the same row index in the increasing order of
row indices and for the same row index in the increasing order of column
indices \n");
                while ( n-- > 0 )
         {
      printf( "Enter the row number, column number, and value\n");
              scanf("%d %d%d",&r,&c,&val);
              s1 = insert ( s1,r,c,val);
         }
   printf("Enter the number of non-zero terms in the sparse matrix1 \n");
         scanf("%d",&n);
         printf("Enter the terms in the sparse matrix2 in the increasing
order of row indices and for the same row index in the increasing order of
row indices and for the same row index in the increasing order of column
indices \n");
         while ( n-- > 0 )
         {
      printf( "Enter the row number, column number, and value\n");
              scanf("%d %d%d",&r,&c,&val);
              s2 = insert ( s2,r,c,val);
         }
         result = sadd(s1,s2);
         printf("The result of addition is\n");
         printlist ( result );
   }

Explanation

1. In order to add two sparse matrices represented using the sorted linked lists as shown in the preceding program, the lists are traversed until the end of one of the lists is reached.
2. In the process of traversal, the row indices stored in the nodes of these lists are compared. If they don't match, a new node is created and inserted into the resultant list by copying the contents of a node with a lower value of row index. The pointer in the list containing a node with a lower value of row index is advanced to make it point to the next node.
3. If the row indices match, column indices for the corresponding row positions are compared. If they don't match, a new node is created and inserted into the resultant list by copying the contents of a node with a lower value of column index. The pointer in the list containing a node with a lower value of column index is advanced to make it point to the next node.
4. If the column indices match, a new node is created and inserted into the resultant list by copying the row and column indices from any of the nodes and the value equal to the sum of the values in the two nodes.
5. After this, the pointers in both the lists are advanced to make them point to the next nodes in the respective lists. This process is repeated in each iteration. After reaching the end of any one of the lists, the iterations come to an end and the remaining nodes in the list whose end has not been reached are copied, as it is in the resultant list.

Example