问验证二进制搜索树- JavaScript

EN

function BinarySearchTree(value) {
  this.val = value;
  this.left = null;
  this.right = null;
}

//insert

BinarySearchTree.prototype.insert = function (toInsert) {

  if (this.val > toInsert) {
    if (this.left === null) {
      this.left = new BinarySearchTree(toInsert);
    } else {
      this.left.insert(toInsert);
    }
  }

  if (this.val < toInsert) {
    if (this.right === null) {
      this.right = new BinarySearchTree(toInsert);
    } else {
      this.right.insert(toInsert);
    }
  }
};


function checkBST(node) {
  // console.log(node.right);
  return isValidBST(node, null, null);
}

function isValidBST(node, min, max) {
  // console.log(min, max);

  //this keeps getting called
  if (node === null) {
    console.log("CHECKING NULL");
    return true;
  }
  // this doesn't get called, which is good 
  if ((min !== null && node.val > max) || (max !== null && node.val < min)) {
    console.log("CHECKING NODE VALUES in false", node.val);
    return false;
  }
  //these calls are never entered.
  if (!checkBST(node.left, min, node.val) || !checkBST(node.right, node.val, max)) {
    console.log("CHECKING NODE VALUES in recursive call", node.val);
    return false;
  }
  return true;
}



var bst = new BinarySearchTree(7);
bst.insert(9);
bst.insert(6);
bst.insert(4);


console.log(checkBST(bst));