var displayTree = (tree) => console.log(JSON.stringify(tree, null, 2));
function Node(value) {
  this.value = value;
  this.left = null;
  this.right = null;
}
function BinarySearchTree() {
  this.root = null;
  // Only change code below this line
  this.findMinHeight = () => {
    let height = -1;
    if (this.root === null) return height;
    let q = [this.root];
    let nextQ = [];
    while (q.length) {
      height++;
      for (let node of q) {
        if (node.left === null && node.right === null) {
          return height;
        }
        if (node.left !== null) nextQ.push(node.left);
        if (node.right !== null) nextQ.push(node.right);
      }
      q = nextQ;
      nextQ = [];
    }
    return height;
  };
  this.findMaxHeight = () => {
    let height = -1;
    if (this.root === null) return height;
    let q = [this.root];
    let nextQ = [];
    while (q.length) {
      height++;
      for (let node of q) {
        if (node.left !== null) nextQ.push(node.left);
        if (node.right !== null) nextQ.push(node.right);
      }
      q = nextQ;
      nextQ = [];
    }
    return height;
  };
  this.isBalanced = () => {
    return this.findMaxHeight() - this.findMinHeight() < 2;
  };
  // Only change code above this line
}