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(0), 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 = 0;
    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-1);
    root->right = buildtree(in, pre, index+1, end);
    return root;
}

int main() {
    char in[6] = {'D', 'B', 'E', 'A', 'F', 'C'};
    char pre[6] = {'A', 'B', 'D', 'E', 'C', 'F'};
    int len = 6;
    node *root = buildtree(in, pre, 0, len-1);
    prints(root);
    return 0;
}