java - Trying to print top view of a tree using two if statements -

problem statement

you given pointer root of binary tree. print top view of binary tree. have complete function.

my code:

void top_view(node root)  {          node r = root;         if(r.left!=null){           top_view(r.left);           system.out.print(r.data + " ");         }        if(r.right!=null){           system.out.print(r.data + " ");           top_view(r.right);         } } 

the 2 if statements executed every time function called, need 1 of them execute. tried switch giving constant expression error. have found different solution problem.

so want know if can make 1 if execute @ time i.e, there way fix code without changing approach?

problem link: https://www.hackerrank.com/challenges/tree-top-view

this problem can solved using:

stack: print root , left subtree.

queue: print right subtree.

your function should this:

 void topview(node root)  {      if(root==null)       return;      stack<integer> s=new stack<integer>();      s.push(root.data);      node root2=root;      while(root.left!=null)      {       s.push(root.left.data);       root=root.left;      }      while(s.size()!=0)       system.out.print(s.pop()+" ");       queue<integer> q=new linkedlist<integer>();       q.add(root2.right.data);      root2=root2.right;           while(root2.right!=null)      {       q.add(root2.right.data);       root2=root2.right;      }      while(q.size()!=0)       system.out.print(q.poll()+" ");  }