Write pseudocode to add a new node to a Binary Search Tree (BST) 

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Here is a C code to construct a BST right from scratch... 


#include <stdio.h> 

typedef struct node 
{ 
  int value; 
  struct node *right; 
  struct node *left; 
}mynode; 

mynode *root; 

add_node(int value); 
void postorder(mynode *root); 
void inorder(mynode *root); 
void preorder(mynode *root); 

int main(int argc, char* argv[]) 
{ 
  root = NULL; 
   
  add_node(5); 
  add_node(1); 
  add_node(-20); 
  add_node(100); 
  add_node(23); 
  add_node(67); 
  add_node(13); 
   
  printf("\nPreorder    : "); 
  preorder(root); 
  printf("\n\nPostorder : "); 
  postorder(root); 
  printf("\n\nInorder   : "); 
  inorder(root); 

  return(0); 
} 

// Function to add a new node... 
add_node(int value) 
{ 
   mynode *prev, *cur, *temp; 
    
   temp        = (mynode *) malloc(sizeof(mynode)); 
   temp->value = value; 
   temp->right = NULL; 
   temp->left = NULL; 

   if(root==NULL) 
   { 
     printf("\nCreating the root..\n"); 
     root = temp; 
     return; 
   } 

   prev=NULL; 
   cur=root; 

   while(cur!=NULL) 
   { 
      prev=cur; 
      cur=(value<cur->value)?cur->left:cur->right; 
   } 

   if(value < prev->value) 
     prev->left=temp; 
   else 
     prev->right=temp; 
} 



void preorder(mynode *root) 
{ 
  if(root) 
  { 
    printf("[%d] ", root->value); 
    preorder(root->left); 
    preorder(root->right); 
  } 
} 


void postorder(mynode *root) 
{ 
  if(root) 
  { 
    postorder(root->left); 
    postorder(root->right); 
    printf("[%d] ", root->value); 
  } 
} 




void inorder(mynode *root) 
{ 
  if(root) 
  { 
    inorder(root->left); 
    printf("[%d] ", root->value); 
    inorder(root->right); 
  } 
}