Duyệt cây nhị phân - Binary Search Tree Traversal

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

struct TreeNode;
typedef struct TreeNode *node;
typedef int ElementType;

struct TreeNode
{
 int element;
 node left, right;
}*root;

node insert(ElementType x,node t)
{
 if(t==NULL)
 {
  t = malloc(sizeof(node));
  t->element = x;
  t->left = t->right = NULL;
 }
 else
 {
  if(x < t->element)
   t->left = insert(x, t->left);
  else if(x > t->element)
   t->right = insert(x, t->right);
 }
 return t;
}

void printpreorder(node T)
{
 if(T != NULL)
 {
  printf("%d ", T->element);
  printpreorder(T->left);
  printpreorder(T->right);
 }
}

void printinorder(node T)
{
 if(T != NULL)
 {
  printinorder(T->left);
  printf("%d ", T->element);
  printinorder(T->right);
 }
}

void printpostorder(node T)
{
 if(T != NULL)
 {
  printpostorder(T->left);
  printpostorder(T->right);
  printf("%d ", T->element);
 }
}

void main()
{
 int ch;
 ElementType a;
 root = NULL;
 while(1)
 {
  clrscr();
  printf("\n1. Insert\n2. Print Pre Order\n3. Print In Order\n4. Print Post Order\n5. Exit\nEnter Your Choice : ");
  scanf("%d",&ch);
  switch(ch)
  {
   case 1:
    printf("Enter an element : ");
    scanf("%d", &a);
    root = insert(a, root);
    break;
   case 2:
    printpreorder(root);
    break;
   case 3:
    printinorder(root);
    break;
   case 4:
    printpostorder(root);
    break;
   case 5:
    exit(0);
   default:
    printf("Invalid Choice");
  }
  getch();
 }
}

Sample Output:

1. Insert
2. Print Pre Order
3. Print In Order
4. Print Post Order
5. Exit
Enter Your Choice : 1
Enter an Element : 1

1. Insert
2. Print Pre Order
3. Print In Order
4. Print Post Order
5. Exit
Enter Your Choice : 1
Enter an Element : 5

1. Insert
2. Print Pre Order
3. Print In Order
4. Print Post Order
5. Exit
Enter Your Choice : 1
Enter an Element : 2

1. Insert
2. Print Pre Order
3. Print In Order
4. Print Post Order
5. Exit
Enter Your Choice : 1
Enter an Element : 7

1. Insert
2. Print Pre Order
3. Print In Order
4. Print Post Order
5. Exit
Enter Your Choice : 2
1 2 5 7

1. Insert
2. Print Pre Order
3. Print In Order
4. Print Post Order
5. Exit
Enter Your Choice : 3
1 5 2 7

1. Insert
2. Print Pre Order
3. Print In Order
4. Print Post Order
5. Exit
Enter Your Choice : 4
2 7 5 1

1. Insert
2. Print Pre Order
3. Print In Order
4. Print Post Order
5. Exit
Enter Your Choice : 5