Data Structure Binary Tree: Construct Full Binary Tree from given preorder and postorder traversals

http://www.geeksforgeeks.org/full-and-complete-binary-tree-from-given-preorder-and-postorder-traversals/

 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     prints(root->left);

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

22     prints(root->right);

23 }

24 

25 node *_buildtree(int pre[], int post[], int &preindex, int l, int h, int size) {

26     if (preindex >= size || l > h) return NULL;

27     node *root = new node(pre[preindex++]);

28     if (l == h) return root;

29     int i = l;

30     for (; i <= h; i++) if (pre[preindex] == post[i]) break;

31     if (i <= h) {

32         root->left = _buildtree(pre, post, preindex, l, i, size);

33         root->right = _buildtree(pre, post, preindex, i+1, h, size);

34     }

35     return root;

36 }

37 

38 node *buildtree(int pre[], int post[], int size) {

39     int preindex = 0;

40     return _buildtree(pre, post, preindex, 0, size-1, size);

41 }

42 

43 int main() {

44     int pre[9] = {1, 2, 4, 8, 9, 5, 3, 6, 7};

45     int post[9] = {8, 9, 4, 5, 2, 6, 7, 3, 1};

46     node *root = buildtree(pre, post, 9);

47     prints(root);

48     return 0;

49 }