Add binary search tree.

Author: trekhleb

README.md

@@ -31,3 +31,8 @@ npm test
 ```
 npm test -- -t 'LinkedList'
 ```
+
+## Useful Links
+
+- [Data Structures and Algorithms on YouTube](https://www.youtube.com/playlist?list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8)
+

src/data-structures/README.md

@@ -1,9 +1,5 @@
 # Data Structures
 
-**Useful Links**
-
-- [YouTube Playlist](https://www.youtube.com/playlist?list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8)
-
 ## Common Data Structure Operations
 
 ![Common Data Structure Operations](https://github.com/trekhleb/javascript-algorithms/blob/master/assets/big-o-data-structures.png)

src/data-structures/tree/BinaryTreeNode.js

@@ -1,7 +1,7 @@
 export default class BinaryTreeNode {
-  constructor(value = null, left = null, right = null) {
-    this.left = left;
-    this.right = right;
+  constructor(value = null) {
+    this.left = null;
+    this.right = null;
     this.value = value;
   }
 

src/data-structures/tree/__test__/BinaryTreeNode.test.js

@@ -26,7 +26,11 @@ describe('BinaryTreeNode', () => {
   it('should traverse node', () => {
     const leftNode = new BinaryTreeNode(1);
     const rightNode = new BinaryTreeNode(3);
-    const rootNode = new BinaryTreeNode(2, leftNode, rightNode);
+    const rootNode = new BinaryTreeNode(2);
+
+    rootNode
+      .addLeft(leftNode)
+      .addRight(rightNode);
 
     expect(rootNode.traverseInOrder()).toEqual([1, 2, 3]);
 

src/data-structures/tree/binary-search-tree/BinarySearchTreeNode.js

@@ -21,20 +21,32 @@ export default class BinarySearchTreeNode extends BinaryTreeNode {
     return this;
   }
 
-  contains(value) {
+  find(value) {
     // Check the root.
     if (this.value === value) {
-      return true;
+      return this;
     }
 
     if (value < this.value && this.left) {
       // Check left nodes.
-      return this.left.contains(value);
+      return this.left.find(value);
     } else if (value > this.value && this.right) {
       // Check right nodes.
-      return this.right.contains(value);
+      return this.right.find(value);
+    }
+
+    return null;
+  }
+
+  contains(value) {
+    return !!this.find(value);
+  }
+
+  findMin() {
+    if (!this.left) {
+      return this;
     }
 
-    return false;
+    return this.left.findMin();
   }
 }

src/data-structures/tree/binary-search-tree/__test__/BinarySearchTreeNode.test.js

@@ -56,4 +56,31 @@ describe('BinarySearchTreeNode', () => {
     expect(bstNode.contains(1)).toBeTruthy();
     expect(bstNode.contains(3)).toBeFalsy();
   });
+
+  it('should find min node', () => {
+    const node = new BinarySearchTreeNode(10);
+
+    node.insert(20);
+    node.insert(30);
+    node.insert(5);
+    node.insert(40);
+    node.insert(1);
+
+    expect(node.findMin()).not.toBeNull();
+    expect(node.findMin().value).toBe(1);
+  });
+
+  it('should find node', () => {
+    const node = new BinarySearchTreeNode(10);
+
+    node.insert(20);
+    node.insert(30);
+    node.insert(5);
+    node.insert(40);
+    node.insert(1);
+
+    expect(node.find(6)).toBeNull();
+    expect(node.find(5)).not.toBeNull();
+    expect(node.find(5).value).toBe(5);
+  });
 });