/*-------------------------------------------------------------------*/
/* fall03exam2q1intel.c                                              */
/*-------------------------------------------------------------------*/

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

struct tree {
   int key;
   struct tree *left;
   struct tree *right;
};

void clearkeys(struct tree *t);

/*-------------------------------------------------------------------*/

void printkeys(struct tree *t) 

/* Print all of the integers in t to stdout. */

{
   if (t != NULL) 
   {
      printkeys(t->left);
      printf("%d\n", t->key);
      printkeys(t->right);
   }
}

/*-------------------------------------------------------------------*/

int main(void)

/* Create a three-level tree containing integers, print the tree
   to stdout, set all of the integers to 0, and print the tree 
   again. */

{
   struct tree *mytree;
   
   mytree = (struct tree*)malloc(sizeof(struct tree));
   mytree->key = 4;
   mytree->left = (struct tree*)malloc(sizeof(struct tree));
   mytree->right = (struct tree*)malloc(sizeof(struct tree));

   mytree->left->key = 2;
   mytree->left->left = (struct tree*)malloc(sizeof(struct tree));
   mytree->left->right = (struct tree*)malloc(sizeof(struct tree));

   mytree->right->key = 6;
   mytree->right->left = (struct tree*)malloc(sizeof(struct tree));
   mytree->right->right = (struct tree*)malloc(sizeof(struct tree));

   mytree->left->left->key = 1;
   mytree->left->left->left = NULL;
   mytree->left->left->right = NULL;

   mytree->left->right->key = 3;
   mytree->left->right->left = NULL;
   mytree->left->right->right = NULL;

   mytree->right->left->key = 5;
   mytree->right->left->left = NULL;
   mytree->right->left->right = NULL;

   mytree->right->right->key = 7;
   mytree->right->right->left = NULL;
   mytree->right->right->right = NULL;

   printkeys(mytree);

   clearkeys(mytree);

   printkeys(mytree);

   return 0;
}