Question

I am stuck on a data structure problem, I am just going off of Geeks for Geeks for help but I need to print 100 random numbers in the range of [1-200]. I can currently only print 5 numbers.

Here is my code:

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
using namespace std;

//binary tree has data & left and right child
struct node{
int data;
struct node *left;
struct node *right;
};

//create a new node
struct node* newNode (int data){
struct node* temp = (struct node *) malloc( sizeof(struct node) );

temp->data = data;
temp->left = temp->right = NULL;

return temp;
}

//recursively creates tree
struct node* constructTreeUtil( int pre[], int* preIndex, int key,
int min, int max, int size ){
if( *preIndex >= size )
return NULL;

struct node* root = NULL;

if( key > min && key < max ){
//allocate memory
root = newNode ( key );
*preIndex = *preIndex + 1;

if (*preIndex < size){
//create subtree under root
root->left = constructTreeUtil( pre, preIndex, pre[*preIndex],
min, key, size );

//right subtree
root->right = constructTreeUtil( pre, preIndex, pre[*preIndex],
key, max, size );
}
}

return root;
}

struct node *constructTree (int pre[], int size){
int preIndex = 0;
return constructTreeUtil ( pre, &preIndex, pre[0], INT_MIN,
INT_MAX, size );
}

void printPreorder(node* node){
if(node==NULL){
return;
}
printf("%d ",node->data);
printPreorder(node->left);
printPreorder(node->right);
}

void printInorder (struct node* node){
if (node == NULL)
return;
printInorder(node->left);
printf("%d ", node->data);
printInorder(node->right);
}

void printPostorder(struct node* node){
if(node==NULL){
return;
}
printPostorder(node->left);
printPostorder(node->right);
printf("%d ", node->data);
}

int main (){
int pre[100];
//filling pre with random numbers
for(int i=0;i<100;i++){
pre[i]=rand()%200+1;
}

int size= sizeof(pre)/sizeof(pre[0]);

struct node *root = constructTree(pre, size);
printf("Preorder traversal of the constructed tree: \n");
printPreorder(root);
printf("\n");
printf("Inorder traversal of the constructed tree: \n");
printInorder(root);
printf("\n");
printf("Postorder traversal of the constructed tree: \n");
printPostorder(root);
printf("\n");

return 0;
}

Answer 1

/*
 *  C - Program to illustrate Traversals in Tree
 */

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

//binary tree has data & left and right child
struct node
{
  int data;
  struct node *left;
  struct node *right;
};

//create a new node
struct node* newNode (int data)
{
  struct node* temp = (struct node *) malloc( sizeof(struct node) );

  temp->data = data;
  temp->left = temp->right = NULL;

  return temp;
}

void constructTreeUtil(struct node* root, int post[], int start, int end)
{
   if (start >= end)
      return;

   int i;
   for (i = start; i < end; ++i) 
      if (post[i] > root->data)
         break;
   
   // left
   if (i > start) {
      root->left = newNode(post[i - 1]);
      constructTreeUtil(root->left, post, start, i - 1);
   }

   // right
   if (i >= start) {
      root->right = newNode(post[end - 1]);
      constructTreeUtil(root->right, post, i, end - 1);
   }
}

struct node* constructTree(int post[], int size)
{
   struct node* root = newNode(post[size - 1]);

   constructTreeUtil(root, post, 0, size - 1);

   return root;
}

void printPreorder(struct node* node)
{
  if(node==NULL)
  {
    return;
  }

  printf("%d ",node->data);
  printPreorder(node->left);
  printPreorder(node->right);
}

void printInorder (struct node* node)
{
  if (node == NULL)
  return;
  printInorder(node->left);
  printf("%d ", node->data);
  printInorder(node->right);
}

void printPostorder(struct node* node)
{
  if(node == NULL)
  {
    return;
  }
  printPostorder(node->left);
  printPostorder(node->right);
  printf("%d ", node->data);
}


int main ()
{
  int pre[100];
  
  srand(time(NULL));

  //filling pre with random numbers
  for(int i = 0; i < 100; i++)
  {
    pre[i] = rand()%200 + 1;
  }

  int size = sizeof(pre)/sizeof(pre[0]);

  struct node *root = constructTree(pre, size);
  printf("Preorder traversal of the constructed tree: \n");
  printPreorder(root);
  printf("\n");
  printf("Inorder traversal of the constructed tree: \n");
  printInorder(root);
  printf("\n");
  printf("Postorder traversal of the constructed tree: \n");
  printPostorder(root);
  printf("\n");

  return 0;
}
/*  Program ends here */