c++ - Constructing Binary tree from given inorder and preorder traversals -

i making binary tree given inorder , preorder traversal array , don't know why giving me wrong output although works points in given array

#include<iostream>  using namespace std;  class node {     public:         int i;         node* left;         node* right;         bool isthreaded;         node(int j); };  node::node(int j):i(j) {     left=null;     right=null; }  void inorder(node* root) {     if(root)     {         inorder(root->left);         cout<<root->i<<"  ";         inorder(root->right);     } }  int findkey(int* a, int l, int r, int key) {     for(int i=l; i<r; i++)     {         if(a[i]==key)             return i;     }      return -1; }  node* constructfrompreorderinorder(int* pre, int n, int* in, int l, int  r, int& k) {     node* root=null;      if(k<n && l<r)     {         int key=findkey(in, l, r, pre[k]); //finds index of current preorder element in inorder array           root=new node(pre[k++]); //forms node          root->left=constructfrompreorderinorder(pre, n, in, 0, key, k); //to find left subtree traverse left of index of element in inroder array          root->right=constructfrompreorderinorder(pre, n, in, key+1, r, k);         //similarly traverse right form right subtree     }     return root; }  int main() {     int pre[]={1,2,4,5,3,6,7};     int in[]={4,2,5,1,6,3,7};      int n=sizeof(pre)/sizeof(*pre); //function used find no. of elements in array. in case elements in preorder array. both same can use      int i=0;     node* root2=constructfrompreorderinorder(pre, n, in, 0, n, i);     inorder(root2); } 

although works the half of elements in array after gives unusual results. have added print statements better view.

please see if helps.

for constructing left subtree range should start l instead of 0.

root->left=constructfrompreorderinorder(pre, n, in, l, key, k);

instead of

root->left=constructfrompreorderinorder(pre, n, in, 0, key, k);