Data Structure Binary Tree: Construct Tree from given Inorder and Preorder traversals

http://www.geeksforgeeks.org/construct-tree-from-given-inorder-and-preorder-traversal/

 #include <iostream>
 #include <vector>
 #include <algorithm>
 #include <queue>
 #include <stack>
 #include <string>
 #include <fstream>
 using namespace std;
 
 struct node {
     char data;
     struct node *left, *right;
     node() : data(), left(NULL), right(NULL) { }
     node(int d) : data(d), left(NULL), right(NULL) { }
 };
 
 void prints(node *root) {
     if (!root) return;
     prints(root->left);
     cout << root->data << " ";
     prints(root->right);
 }
 
 node *buildtree(char in[], char pre[], int beg, int end) {
     static int preindex = ;
     if (beg > end) return NULL;
     node *root = new node(pre[preindex++]);
     int index = beg;
     for (int i = beg; i <= end; i++) {
         if (in[i] == root->data) {
             index = i;
             break;
         }
     }
     root->left = buildtree(in, pre, beg, index-);
     root->right = buildtree(in, pre, index+, end);
     return root;
 }
 
 int main() {
     char in[] = {'D', 'B', 'E', 'A', 'F', 'C'};
     char pre[] = {'A', 'B', 'D', 'E', 'C', 'F'};
     int len = ;
     node *root = buildtree(in, pre, , len-);
     prints(root);
     return ;
 }