Data Structure Binary Tree: Iterative Postorder Traversal

http://www.geeksforgeeks.org/iterative-postorder-traversal-using-stack/

 1 #include <iostream>

 2 #include <vector>

 3 #include <algorithm>

 4 #include <queue>

 5 #include <stack>

 6 #include <string>

 7 #include <fstream>

 8 #include <map>

 9 using namespace std;

10 

11 struct node {

12     int data;

13     struct node *left, *right;

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

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

16 };

17 

18 void prints(node *root) {

19     if (!root) return;

20     stack<node*> S;

21     do {

22         while (root) {

23             if (root->right) S.push(root->right);

24             S.push(root);

25             root = root->left;

26         }

27         root = S.top();

28         S.pop();

29         if (root->right && !S.empty() && root->right == S.top()) {

30             S.pop();

31             S.push(root);

32             root = root->right;

33         }

34         else {

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

36             root = NULL;

37         }

38     } while (!S.empty());

39 }

40 

41 int main() {

42     node *root = new node(1);

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

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

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

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

47     root->right->left = new node(6);

48     root->right->right = new node(7);

49     prints(root);

50     return 0;

51 }