From 873024079a38948ab10292a73130235bca65ae43 Mon Sep 17 00:00:00 2001
From: Oleksii Trekhleb <trehleb@gmail.com>
Date: Tue, 3 Apr 2018 06:41:45 +0300
Subject: [PATCH] Add binary search tree.

---
 .../binary-search-tree/BinarySearchTreeNode.js    |  4 ++--
 .../__test__/BinarySearchTreeNode.test.js         | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/data-structures/tree/binary-search-tree/BinarySearchTreeNode.js b/src/data-structures/tree/binary-search-tree/BinarySearchTreeNode.js
index 5ee5e788..d298c722 100644
--- a/src/data-structures/tree/binary-search-tree/BinarySearchTreeNode.js
+++ b/src/data-structures/tree/binary-search-tree/BinarySearchTreeNode.js
@@ -9,7 +9,7 @@ export default class BinarySearchTreeNode extends BinaryTreeNode {
       } else {
         this.left = new BinarySearchTreeNode(value);
       }
-    } else {
+    } else if (value > this.value) {
       // Insert to the right.
       if (this.right) {
         this.right.insert(value);
@@ -30,7 +30,7 @@ export default class BinarySearchTreeNode extends BinaryTreeNode {
     if (value < this.value && this.left) {
       // Check left nodes.
       return this.left.contains(value);
-    } else if (this.right) {
+    } else if (value > this.value && this.right) {
       // Check right nodes.
       return this.right.contains(value);
     }
diff --git a/src/data-structures/tree/binary-search-tree/__test__/BinarySearchTreeNode.test.js b/src/data-structures/tree/binary-search-tree/__test__/BinarySearchTreeNode.test.js
index 0ff84dfd..1191301e 100644
--- a/src/data-structures/tree/binary-search-tree/__test__/BinarySearchTreeNode.test.js
+++ b/src/data-structures/tree/binary-search-tree/__test__/BinarySearchTreeNode.test.js
@@ -41,4 +41,19 @@ describe('BinarySearchTreeNode', () => {
     expect(bstNode.contains(6)).toBeTruthy();
     expect(bstNode.contains(8)).toBeFalsy();
   });
+
+  it('should not insert duplicates', () => {
+    const bstNode = new BinarySearchTreeNode(2);
+    bstNode.insert(1);
+
+    expect(bstNode.toString()).toBe('1,2');
+    expect(bstNode.contains(1)).toBeTruthy();
+    expect(bstNode.contains(3)).toBeFalsy();
+
+    bstNode.insert(1);
+
+    expect(bstNode.toString()).toBe('1,2');
+    expect(bstNode.contains(1)).toBeTruthy();
+    expect(bstNode.contains(3)).toBeFalsy();
+  });
 });