Tree traversal의 3가지

1. 전위 순회 (Preorder Traversal)

Root -> Left Tree -> Right Tree   ( 루트를 제일 처음에 방문 )

2. 중위 순회 (Inorder Traversal)

Left Tree -> Root -> Right Tree   ( 루트를 중간에 방문 )

3. 후위 순회 (Postorder Traversal)

Left Tree -> Right Tree -> Root   ( 루트를 제일 마지막에 방문 )

<소스코드>
출처 : http://www.geeksforgeeks.org/tree-traversals-inorder-preorder-and-postorder

/// C program for different tree traversals
#include <stdio.h>
#include <stdlib.h>

/* A binary tree node has data, pointer to left child
   and a pointer to right child */
struct node
{
     int data;
     struct node* left;
     struct node* right;
};

/* Helper function that allocates a new node with the
   given data and NULL left and right pointers. */
struct node* newNode(int data)
{
     struct node* node = (struct node*)
                                  malloc(sizeof(struct node));
     node->data = data;
     node->left = NULL;
     node->right = NULL;

     return(node);
}

/* Given a binary tree, print its nodes according to the
  "bottom-up" postorder traversal. */
void printPostorder(struct node* node)
{
     if (node == NULL)
        return;

     // first recur on left subtree
     printPostorder(node->left);

     // then recur on right subtree
     printPostorder(node->right);

     // now deal with the node
     printf("%d ", node->data);
}

/* Given a binary tree, print its nodes in inorder*/
void printInorder(struct node* node)
{
     if (node == NULL)
          return;

     /* first recur on left child */
     printInorder(node->left);

     /* then print the data of node */
     printf("%d ", node->data);

     /* now recur on right child */
     printInorder(node->right);
}

/* Given a binary tree, print its nodes in preorder*/
void printPreorder(struct node* node)
{
     if (node == NULL)
          return;

     /* first print data of node */
     printf("%d ", node->data);

     /* then recur on left sutree */
     printPreorder(node->left);

     /* now recur on right subtree */
     printPreorder(node->right);
} 

/* Driver program to test above functions*/
int main()
{
     struct node *root  = newNode(1);
     root->left             = newNode(2);
     root->right           = newNode(3);
     root->left->left     = newNode(4);
     root->left->right   = newNode(5);

     printf("\nPreorder traversal of binary tree is \n");
     printPreorder(root);

     printf("\nInorder traversal of binary tree is \n");
     printInorder(root);

     printf("\nPostorder traversal of binary tree is \n");
     printPostorder(root);

     getchar();
     return 0;
}