text: class Node {
    constructor(val) {
      this.val = val;
      this.left = null;
      this.right = null;
    }
  }
  
  /*
              a
            /    \
           b       c
          / \       \ 
         d   e       f
  
            */
  
  const a = new Node("a");
  const b = new Node("b");
  const c = new Node("c");
  const d = new Node("d");
  const e = new Node("e");
  const f = new Node("f");
  
  a.left = b;
  a.right = c;
  b.left = d;
  b.right = e;
  c.right = f;
  
  
  /*
              a
            /    \
           b       c
          / \       \ 
         d   e       f
  
            */
  
  // using preorder
  function binary_tree_diameter(root) {
    if (root===null) return;
    let result = []
    let count  = 0
    const stack = [root];
    while (stack.length > 0){
      const current = stack.pop();
    
    }
  }
  
  console.log(binary_tree_diameter(a));
  