이진트리

typedef struct node* tree_pointer;
typedef struct node{
 int data;
 tree_pointer left_child,right_child;
};

//중위순회
void inorder(tree_pointer ptr)
{
 if(ptr){
  inorder(ptr->left_child);
  printf("%d\n",ptr->data);
  inorder(ptr->right_child);
 }
}

//전위순회
void preorder(tree_pointer ptr)
{
 if(ptr){
  printf("%d\n",ptr->data);
  preorder(ptr->left_child);
  preorder(ptr->right_child);
 }
}

//후위순회
void postorder(tree_pointer ptr)
{
 if(ptr){
  postorder(ptr->left_child);
  postorder(ptr->right_child);
  printf("%d\n",ptr->data);
 }
}

//반복적인 중위순회(stack)
void iter_inorder(tree_pointer node)
{
 int top = -1;
 tree_pointer stack[MAX_STACK_SIZE];
 for( ; ; ){
  for( ; node; node->left_child)
   add(&top,node);
  node = delete(&top);
  if(!node) break;
  printf("%d\n", ptr->data);
  node = node->right_child;
 }
}

//레벨순서 트리 순회
void level_order(tree_pointer ptr)
{
 int front,rear = 0;
 tree_pointer queue[MAX_QUEUE_SIZE];
 if (!ptr) return;
 addq(front, &rear, ptr);
 for( ; ; ){
  ptr = deleteq(&front, rear);
  if(ptr){
   printf("%d\n",ptr->data);
   if(ptr->left_child)
    addq(front,&rear,ptr->left_child);
   if(ptr->right_child)
    addq(front,&rear,ptr->right_child);
  }
  else break;
 }
}

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

typedef struct Treenode{
 int data;
 struct Treenode *left,*right;
}Treenode;

Treenode n1={4,NULL,NULL};
Treenode n2={2,&n1,NULL};
Treenode n3={5,NULL,NULL};
Treenode n4={6,NULL,NULL};
Treenode n5={3,&n3,&n4};
Treenode n6={1,&n2,&n5};

Treenode* root = &n6;

inorder(Treenode *root){
 if(root){
  inorder(root->left);
  printf("%d->",root->data);
  inorder(root->right);
 }
}

preorder(Treenode* root){
 if(root){
  printf("%d->",root->data);
  preorder(root->left);
  preorder(root->right);
 }
}

postorder(Treenode* root){
 if(root){
  postorder(root->left);
  postorder(root->right);
  printf("%d->",root->data);
 }
}

void main()
{
 printf("중위순회 : ");
 inorder(root);
 printf("\n");
 printf("전위순회 : ");
 preorder(root);
 printf("\n");
 printf("후위순회 : ");
 postorder(root);
 printf("\n");
}