Flatten BST to sorted list

 // Flatten BST to Sortlisted

#include<bits/stdc++.h>

using namespace std;

struct Node{

    int data;

    struct Node* left;

    struct Node* right;

    Node(int val){

        data=val;

        left=NULL;

        right=NULL;

    }

};

void fun(Node* parent){

    Node* curr = parent;

    while (curr != NULL)

        cout << curr->data << " ", curr = curr->right;

}

void inorder(Node* curr, Node* & prev){

    if(!curr) return;

    inorder(curr->left, prev);

    prev->left=NULL;

    prev->right=curr;

    prev=curr;

    inorder(curr->right, prev);

}

Node* flatten(Node* root){

    Node* dummy=new Node(-1);

    Node* prev=dummy;

    inorder(root, prev);

    prev->left=NULL;

    prev->right=NULL;

    Node* ret=dummy->right;

    return ret;

}

int main(){

       #ifndef ONLINE_JUDGE

freopen("input.txt", "r", stdin);

freopen("output.txt", "w", stdout);

#endif

      struct Node* root=new Node(5);

      root->left=new Node(3);

      root->left->left=new Node(2);

      root->left->right=new Node(4);

      root->right=new Node(7);

      root->right->left=new Node(6);

      root->right->right=new Node(8);

      fun(flatten(root));

    return 0;

}