preorder

1void preorder(Node* root){
2    if(root != NULL){
3        cout<<root->data<<" ";
4        preorder(root->left);
5        preorder(root->right);
6    }
7}

1#include <iostream>
2using namespace std;
3
4class node{
5public:
6    int data;
7    node* left;
8    node* right;
9
10    node(int d){
11        data = d;
12        left = NULL;
13        right = NULL;
14    }
15};
16
17node* buildTree(){
18    int d;
19    cin>>d;
20
21    if(d==-1){
22        return NULL;	//to attach a NULL pointer[in case of no child] enter -1
23    }
24    node * root = new node(d);
25    root->left = buildTree();
26    root->right = buildTree();
27    return root;
28}
29
30
31
32//REQUIRED FUNCTION: Inorder Traversal
33
34
35void printIn(node*root){
36    if(root==NULL){
37        return;
38    }
39    //Otherwise Left Root Right
40    printIn(root->left);
41    cout<<root->data<<" ";
42    printIn(root->right);
43}
44
45
46int main(){ 
47    node* root = buildTree();
48    printIn(root);
49
50	return 0;
51}
52
53//SAMPLE INPUT TO RUN THE CODE ON ANY ONLINE IDE:
54//8 10 1 -1 -1 6 9 -1 -1 7 -1 -1 3 -1 14 13 -1 -1 -1
55