Added Binary Search Tree Challenge (#35907)

* Added Binary Search Tree Challenge

* fix yaml, fix solutions, fix tests

* Fixed recommended fixes

curriculum/challenges/_meta/data-structures/meta.json

@@ -132,6 +132,10 @@
       "587d8257367417b2b2512c7c",
       "Check if an Element is Present in a Binary Search Tree"
     ],
+    [
+      "5cc0c1b32479e176caf3b422",
+      "Check if Tree is Binary Search Tree"
+    ],
     [
       "587d8257367417b2b2512c7d",
       "Find the Minimum and Maximum Height of a Binary Search Tree"

curriculum/challenges/english/08-coding-interview-prep/data-structures/check-if-binary-search-tree.english.md

@@ -0,0 +1,138 @@
+---
+id: 5cc0c1b32479e176caf3b422
+title: Check if Tree is Binary Search Tree
+challengeType: 1
+---
+
+## Description
+
+<section id='description'>
+Since you already know what a binary search tree is, this challenge will establish how it is you can tell that a tree is a binary search tree or not.
+The main distinction of a binary search tree is that the nodes are ordered in an organized fashion. Nodes have at most 2 child nodes (placed to the right and/or left) based on if the child node's value is greater than or equal to (right) or less than (left) the parent node.
+</section>
+
+## Instructions
+
+<section id='instructions'>
+In this challenge, you will create a utility for your tree. Write a JavaScript method <code>isBinarySearchTree</code> which takes a tree as an input and returns a boolean value for whether the tree is a binary search tree or not. Use recursion whenever possible.
+</section>
+
+## Tests
+
+<section id='tests'>
+
+```yml
+tests:
+  - text: Your Binary Search Tree should return true when checked with <code>isBinarySearchTree()</code>.
+    testString: assert((function() { var test = false; if (typeof BinarySearchTree !== 'undefined') { test = new BinarySearchTree() } else { return false; }; test.push(3); test.push(4); test.push(5); return isBinarySearchTree(test) == true})(), 'Your Binary Search Tree should return true when checked with <code>isBinarySearchTree()</code>.');
+```
+
+</section>
+
+## Challenge Seed
+
+<section id='challengeSeed'>
+
+<div id='js-seed'>
+
+```js
+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;
+}
+function isBinarySearchTree(tree) {
+  // change code below this line
+  // change code above this line
+}
+```
+
+</div>
+
+### After Test
+<div id='js-teardown'>
+
+```js
+BinarySearchTree.prototype.push = function(val) {
+  var root = this.root;
+
+  if (!root) {
+    this.root = new Node(val);
+    return;
+  }
+
+  var currentNode = root;
+  var newNode = new Node(val);
+
+  while (currentNode) {
+    if (val < currentNode.value) {
+      if (!currentNode.left) {
+        currentNode.left = newNode;
+        break;
+      } else {
+        currentNode = currentNode.left;
+      }
+    } else {
+      if (!currentNode.right) {
+        currentNode.right = newNode;
+        break;
+      } else {
+        currentNode = currentNode.right;
+      }
+    }
+  }
+};
+```
+
+</div>
+
+</section>
+
+## Solution
+
+<section id='solution'>
+
+```js
+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;
+}
+function isBinarySearchTree(tree) {
+  if (tree.root == null) {
+    return null;
+  } else {
+    let isBST = true;
+    function checkTree(node) {
+      if (node.left != null) {
+        const left = node.left;
+        if (left.value > node.value) {
+          isBST = false;
+        } else {
+          checkTree(left);
+        }
+      }
+      if (node.right != null) {
+        const right = node.right;
+        if (right.value < node.value) {
+          isBST = false;
+        } else {
+          checkTree(right);
+        }
+      }
+    }
+    checkTree(tree.root);
+    return isBST;
+  }
+};
+```
+
+</section>