Data Structure Binary Tree: Inorder Tree Traversal without recursion and without stack!

http://www.geeksforgeeks.org/inorder-tree-traversal-without-recursion-and-without-stack/

 1 #include <iostream>

 2 #include <vector>

 3 #include <algorithm>

 4 #include <queue>

 5 #include <stack>

 6 #include <string>

 7 #include <fstream>

 8 using namespace std;

 9 

10 struct node {

11     int data;

12     struct node *left, *right;

13     node() : data(0), left(NULL), right(NULL) { }

14     node(int d) : data(d), left(NULL), right(NULL) { }

15 };

16 

17 void print(node *root) {

18     if (!root) return;

19     node *cur = root;

20     while (cur) {

21         if (!cur->left) {

22             cout << cur->data << " ";

23             cur = cur->right;

24         }

25         else {

26             node *pre = cur->left;

27             while (pre->right && pre->right != cur) pre = pre->right;

28             if (pre->right == NULL) {

29                 pre->right = cur;

30                 cur = cur->left;

31             }

32             else {

33                 pre->right = NULL;

34                 cout << cur->data << " ";

35                 cur = cur->right;

36             }

37         }

38     }

39 }

40 

41 void prints(node *root) {

42     if (!root) return;

43     prints(root->left);

44     cout << root->data << " ";

45     prints(root->right);

46 }

47 

48 int main() {

49     node* root = new node(1);

50     root->left = new node(2);

51     root->right = new node(3);

52     root->left->left = new node(4);

53     root->left->right = new node(5);

54     print(root);

55     return 0;

56 }