bst remove root node fix. bst specs.

Author: JakeHP

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

@@ -181,7 +181,7 @@
    * Average time complexity: O(log N).
    *
    * @public
-   * @param {Number|String} Value of the node which should be found.
+   * @param {Number|String} value of the node which should be found.
    */
   exports.BinaryTree.prototype.find = function (value) {
     return this._find(value, this._root);
@@ -192,8 +192,8 @@
    * Average time complexity: O(log N).
    *
    * @private
-   * @param {Number|String} Value of the node which should be found.
-   * @param {Node} Current node to be checked.
+   * @param {Number|String} value of the node which should be found.
+   * @param {Node} current node to be checked.
    */
   exports.BinaryTree.prototype._find = function (value, current) {
     if (!current) {
@@ -232,7 +232,6 @@
       } else {
         parent._right = newChild;
       }
-
       if (newChild) {
         newChild._parent = parent;
       }
@@ -244,7 +243,7 @@
    * Average runtime complexity: O(log N).
    *
    * @public
-   * @param {Node} Node to be removed
+   * @param {Node} node to be removed
    * @returns {Boolean} True/false depending
    *    on whether the given node is removed.
    */
@@ -261,12 +260,16 @@
       min.value = temp;
       return this.remove(min);
     } else {
-      if (node._left) {
-        this._replaceChild(node._parent, node, node._left);
-      } else if (node._right) {
-        this._replaceChild(node._parent, node, node._right);
-      } else {
-        this._replaceChild(node._parent, node, null);
+      if (node._parent !== null) {
+        if (node._left) {
+          this._replaceChild(node._parent, node, node._left);
+        } else if (node._right) {
+          this._replaceChild(node._parent, node, node._right);
+        } else {
+          this._replaceChild(node._parent, node, null);
+        }
+      }else {
+        this._root = null;
       }
       return true;
     }

test/data-structures/binary-search-tree.spec.js

@@ -0,0 +1,77 @@
+'use strict';
+
+var mod = require('../../src/data-structures/binary-search-tree.js');
+var Node = mod.Node;
+var BinaryTree = mod.BinaryTree;
+
+describe('Node', function () {
+  it('should be a constructor function', function () {
+    expect(typeof Node).toBe('function');
+  });
+});
+
+describe('Binary Tree', function () {
+  it('should be a constructor function', function () {
+    expect(typeof BinaryTree).toBe('function');
+  });
+  it('should start with null root', function () {
+    expect(new BinaryTree()._root).toBe(null);
+  });
+  it('should insert and remove single node properly', function () {
+    var bTree = new BinaryTree();
+    bTree.insert(15);
+    var node = bTree.find(15);
+    bTree.remove(node);
+    expect(bTree._root).toBe(null);
+  });
+  it('should insert multiple nodes properly', function () {
+    var bTree = new BinaryTree();
+    bTree.insert(10);
+    bTree.insert(5);
+    bTree.insert(15);
+    bTree.insert(4);
+    bTree.insert(6);
+    bTree.insert(14);
+    bTree.insert(16);
+    var leftRootChild = bTree._root._left;
+    var rightRootChild = bTree._root._right;
+    expect(bTree._root.value).toBe(10);
+    expect(leftRootChild.value).toBe(5);
+    expect(rightRootChild.value).toBe(15);
+    expect(leftRootChild._left.value).toBe(4);
+    expect(leftRootChild._right.value).toBe(6);
+    expect(rightRootChild._left.value).toBe(14);
+    expect(rightRootChild._right.value).toBe(16);
+  });
+  it('should remove multiple nodes properly', function () {
+    var bTree = new BinaryTree();
+    bTree.insert(10);
+    bTree.insert(5);
+    bTree.insert(15);
+    bTree.insert(4);
+    bTree.insert(6);
+    bTree.insert(7);
+    bTree.insert(14);
+    bTree.insert(16);
+    var leftRootChild = bTree._root._left;
+    var rightRootChild = bTree._root._right;
+    var sixteen = bTree.find(16);
+    bTree.remove(sixteen);
+    expect(bTree._root.value).toBe(10);
+    expect(leftRootChild.value).toBe(5);
+    expect(rightRootChild.value).toBe(15);
+    expect(leftRootChild._left.value).toBe(4);
+    expect(leftRootChild._right.value).toBe(6);
+    expect(leftRootChild._right._right.value).toBe(7);
+    expect(rightRootChild._left.value).toBe(14);
+    expect(rightRootChild._right).toBe(null);
+    var fourteen = bTree.find(14);
+    bTree.remove(fourteen);
+    expect(rightRootChild._left).toBe(null);
+    var five = bTree.find(5);
+    bTree.remove(five);
+    expect(leftRootChild.value).toBe(6);
+    expect(leftRootChild._left.value).toBe(4);
+    expect(leftRootChild._right.value).toBe(7);
+  });
+});