Spanning Tree DS and DCN

This program is for implementing Spanning Tree. 


#include<stdio.h>
#include<alloc.h>
#define MAX 20
struct edge
{
 int u;
 int v;
 int weight;
 struct edge *link;
}*front = NULL;

int father[MAX];
struct edge tree[MAX];
int n;
int wt_tree=0;
int count=0;
void make_tree();
void insert_tree(int i,int j,int wt);
void insert_pque(int i,int j,int wt);
void create_graph();
struct edge *del_pque();
void main()
{
 int i;
 clrscr();
 create_graph();
 make_tree();
 printf("\nEdges to be included in spanning tree are :\n");
 for(i=1;i<=count;i++)
 {
  printf("%d->",tree[i].u);
  printf("%d\n",tree[i].v);
 }
 printf("\n\nWeight of this minimum spanning tree is : %d\n", wt_tree);
 getch();
}


void create_graph()
{
 int i,wt,max_edges,origin,destin;
 printf("Enter number of nodes : ");
 scanf("%d",&n);
 max_edges=n*(n-1)/2;
 for(i=1;i<=max_edges;i++)
 {
  printf("Enter edge %d(0 0 to quit): ",i);
  scanf("%d %d",&origin,&destin);
  if( (origin==0) && (destin==0) )
   break;
  printf("Enter weight for this edge : ");
  scanf("%d",&wt);

  if( origin > n || destin > n || origin<=0 || destin<=0)
  {
   printf("Invalid edge!\n");
   i--;
  }
  else
   insert_pque(origin,destin,wt);
 }
}

void make_tree()
{
 struct edge *tmp;
 int node1,node2,root_n1,root_n2;

 while( count < n-1)
 {
  tmp=del_pque();
  node1=tmp->u;
  node2=tmp->v;

  while( node1 > 0)
  {
   root_n1=node1;
   node1=father[node1];
  }


  while( node2 >0 )
  {
   root_n2=node2;
   node2=father[node2];
  }

  if(root_n1!=root_n2)
  {
   insert_tree(tmp->u,tmp->v,tmp->weight);
   wt_tree=wt_tree+tmp->weight;
   father[root_n2]=root_n1;
  }
 }
}

void insert_tree(int i,int j,int wt)
{
 count++;
 tree[count].u=i;
 tree[count].v=j;
 tree[count].weight=wt;
}

void insert_pque(int i,int j,int wt)
{
 struct edge *tmp,*q;

 tmp = (struct edge *)malloc(sizeof(struct edge));
 tmp->u=i;
 tmp->v=j;
 tmp->weight = wt;

 if( front == NULL || tmp->weight < front->weight )
 {
  tmp->link = front;
  front = tmp;
 }


 else
 {
  q = front;
  while(q->link != NULL && q->link->weight <= tmp->weight)
   q=q->link;
  tmp->link = q->link;
  q->link = tmp;

  if(q->link == NULL)
  tmp->link = NULL;
 }
}
struct edge *del_pque()
{
 struct edge *tmp;
 tmp = front;
 front = front->link;
 return tmp;
}