C Program to recontruct a Binary Search Tree

#include<stdio.h>
#include<conio.h>
#include<alloc.h>
#define MAX 101
struct node
{
   struct node *left;
   int data;
   struct node *right;
};
void insert(struct node **,int);
void preorder(struct node *);
void postorder(struct node *);
void inorder(struct node *);
struct node * recons(int*, int *,int);
void deltree(struct node *);
int in[MAX],pre[MAX],x;
void main()
{
   struct node *t,*p,*q;
   int req,i,num;
   t=NULL;  /* Empty Tree */
   clrscr();
   printf(" Specify the number of items to be inserted : ");
   while(1)
   {
      scanf(" %d",&req);
      if(req >= MAX || req <= 0)
  printf("\n Enter number between 1 to 100. \n");
      else
  break;
   }
   for(i=0;i<req;i++)
   {
      printf("\n Enter the data : ");
      scanf("%d",&num);
      insert(&t,num);
   }
   printf("\n In-order Traversal :\n");
   x=0;
   inorder(t);
   printf("\n Pre-order Traversal :\n");
   x=0;
   preorder(t);
   printf("\n Post-order Traversal :\n");
   x=0;
   postorder(t);
   deltree(t);
   t=NULL;
   t=recons(in,pre,req);
   printf("\n\n After reconstruction of the binary tree.\n");
   x=0;
   printf("\n In-order Traversal :\n");
   inorder(t);
   x=0;
   printf("\n Pre-order Traversal :\n");
   preorder(t);
   x=0;
   printf("\n Post-order Traversal :\n");
   postorder(t);
   deltree(t);
   getch();
}

/* Inserts a new node in a binary search tree */
void insert(struct node **sr,int num)
{
   if(*sr == NULL)
   {
       *sr=(struct node *)malloc(sizeof(struct node));
       (*sr)->left=NULL;
       (*sr)->data=num;
       (*sr)->right=NULL;
       return;
   }
   else   /* Search the node to which new node will be attached */
   {
       /* If new data is less , traverse to left */
       if(num < (*sr)->data)
   insert(&((*sr)->left),num);
       else
   /* Else traverse to right */
   insert(&((*sr)->right),num);
   }
 }
 void preorder(struct node *t)
 {
   if(t != NULL)
   {
      printf("%d\t",pre[x++]=t->data);
      preorder(t->left);
      preorder(t->right);
   }
 }
 void postorder(struct node *t)
 {
    if(t!=NULL)
    {
       postorder(t->left);
       postorder(t->right);
       printf("%d\t",t->data);
    }
 }
 void inorder(struct node *t)
 {
    if(t != NULL)
    {
       inorder(t->left);
       printf("%d\t",in[x++]=t->data);
       inorder(t->right);
    }
 }

 struct node * recons(int *inorder,int *preorder,int noofnodes)
 {
    struct node *temp,*left,*right;
    int tempin[100],temppre[100],i,j;
    if(noofnodes == 0)
       return NULL;
    temp=(struct node *)malloc(sizeof(struct node));
    temp->data=preorder[0];
    temp->left=NULL;
    temp->right=NULL;
    if(noofnodes == 1)
       return temp;
    for(i=0;inorder[i]!=preorder[0];)
       i++;
    if(i>0)
    {
       for(j=0;j<=i;j++)
    tempin[j]=inorder[j];
       for(j=0;j<i;j++)
    temppre[j]=preorder[j+1];
    }
    left=recons(tempin,temppre,i);
    temp->left=left;
    if(i<noofnodes -1)
    {
       for(j=i;j<noofnodes;j++)
       {
  tempin[j-i]=inorder[j+1];
  temppre[j-i]=preorder[j+1];
       }
    }
    right=recons(tempin,temppre,noofnodes-i-1);
    temp->right=right;
    return temp;
}
 void deltree(struct node *t)
 {
    if(t!=NULL)
    {
 deltree(t->left);
 deltree(t->right);
    }
    free(t);
 }