Merge pull request #56 from datastructures-js/find_key

allow finding nodes by key

Author: eyas-ranjous

README.md

@@ -15,7 +15,9 @@ Binary Search Tree & AVL Tree (Self Balancing Tree) implementation in javascript
   * [constructor](#constructor)
   * [insert](#insert)
   * [has](#has)
+  * [hasKey](#haskey)
   * [find](#find)
+  * [findKey](#findkey)
   * [min](#min)
   * [max](#max)
   * [lowerBound (floor)](#lowerbound-floor)
@@ -70,6 +72,8 @@ the compare function must return a number for the 3 cases:
 
 There is already a default compare function for primitive values (number, string).
 
+constructor also accepts an options param, where the comparison key prob name can be passed for object types in order to search by that key directly using findKey and hasKey.
+
 ##### JS
 ###### BinarySearchTree
 ```js
@@ -80,7 +84,7 @@ const employees = new BinarySearchTree((a, b) => a.id - b.id);
 ###### AvlTree
 ```js
 const nums = new AvlTree();
-const employees = new AvlTree((a, b) => a.id - b.id);
+const employees = new AvlTree((a, b) => a.id - b.id, { key: 'id' });
 ```
 
 ##### TS
@@ -93,13 +97,13 @@ interface IEmployee {
 ###### BinarySearchTree
 ```js
 const nums = new BinarySearchTree<number>();
-const employees = new BinarySearchTree<IEmployee>((a, b) => a.id - b.id);
+const employees = new BinarySearchTree<IEmployee>((a, b) => a.id - b.id, { key: 'id' });
 ```
 
 ###### AvlTree
 ```js
 const nums = new AvlTree<number>();
-const employees = new AvlTree<IEmployee>((a, b) => a.id - b.id);
+const employees = new AvlTree<IEmployee>((a, b) => a.id - b.id, { key: 'id' });
 ```
 
 ### insert
@@ -140,6 +144,16 @@ employees.has({ id: 50 }); // true
 employees.has({ id: 100 }); // false
 ```
 
+### hasKey
+O(log(n))
+
+checks if a value exists by its key if the node's key prob is provided in the constructor.
+
+```js
+employees.has(50); // true
+employees.has(100); // false
+```
+
 ### find
 O(log(n))
 
@@ -153,6 +167,16 @@ employees.find({ id: 60 }).getValue(); // { id: 60 }
 employees.find({ id: 100 }); // null
 ```
 
+### findKey
+O(log(n))
+
+finds a node by its key if the node's key prob is provided in the constructor.
+
+```js
+employees.findKey(60).getValue(); // { id: 60 }
+employees.find(100); // null
+```
+
 ### min
 O(log(n))
 

src/avlTree.d.ts

@@ -2,9 +2,10 @@ import { BinarySearchTree } from './binarySearchTree';
 import { AvlTreeNode } from './avlTreeNode';
 
 export class AvlTree<T> extends BinarySearchTree<T> {
-  constructor(compare?: (a: T, b: T) => number);
+  constructor(compare?: (a: T, b: T) => number, options?: { key: string });
   insert(value: T): AvlTree<T>;
   find(value: T): AvlTreeNode<T> | null;
+  findKey(key: number|string): AvlTreeNode<T> | null;
   max(node?: AvlTreeNode<T>): AvlTreeNode<T> | null;
   min(node?: AvlTreeNode<T>): AvlTreeNode<T> | null;
   lowerBound(value: T, includeEqual?: boolean): AvlTreeNode<T> | null;

src/avlTree.js

@@ -12,12 +12,12 @@ const { AvlTreeNode } = require('./avlTreeNode');
  * @extends BinarySearchTree
  */
 class AvlTree extends BinarySearchTree {
-  constructor(compare) {
+  constructor(compare, options) {
     if (compare && typeof compare !== 'function') {
       throw new Error('AvlTree constructor expects a compare function');
     }
 
-    super(compare);
+    super(compare, options);
   }
 
   /**

src/binarySearchTree.d.ts

@@ -1,10 +1,12 @@
 import { BinarySearchTreeNode } from './binarySearchTreeNode';
 
 export class BinarySearchTree<T> {
-  constructor(compare?: (a: T, b: T) => number);
+  constructor(compare?: (a: T, b: T) => number, options?: { key: string });
   insert(value: T): BinarySearchTree<T>;
   has(value: T): boolean;
+  hasKey(key: number|string): boolean;
   find(value: T): BinarySearchTreeNode<T> | null;
+  findKey(key: number|string): BinarySearchTreeNode<T> | null;
   max(node?: BinarySearchTreeNode<T>): BinarySearchTreeNode<T> | null;
   min(node?: BinarySearchTreeNode<T>): BinarySearchTreeNode<T> | null;
   lowerBound(value: T, includeEqual?: boolean): BinarySearchTreeNode<T> | null;

src/binarySearchTree.js

@@ -15,12 +15,13 @@ const defaultCompare = (a, b) => {
  * @class BinarySearchTree
  */
 class BinarySearchTree {
-  constructor(compare) {
+  constructor(compare, options) {
     if (compare && typeof compare !== 'function') {
       throw new Error('BinarySearchTree constructor expects a compare function');
     }
 
     this._compare = compare || defaultCompare;
+    this._options = options || {};
     this._root = null;
     this._count = 0;
   }
@@ -65,9 +66,9 @@ class BinarySearchTree {
   }
 
   /**
-   * Checks if a value exists in the tree by its key
+   * Checks if a value exists in the tree by its value
    * @public
-   * @param {number|string} key
+   * @param {number|string|object} value
    * @return {boolean}
    */
   has(value) {
@@ -84,9 +85,22 @@ class BinarySearchTree {
   }
 
   /**
-   * Finds a node by its key
+   * Checks if a value exists in the tree by its key
    * @public
    * @param {number|string} key
+   * @return {boolean}
+   */
+  hasKey(key) {
+    if (this._options.key === undefined || this._options.key === null) {
+      throw new Error('Missing key prop name in constructor options');
+    }
+    return this.has({ [this._options.key]: key });
+  }
+
+  /**
+   * Finds a node by its value
+   * @public
+   * @param {number|string|object} value
    * @return {BinarySearchTreeNode}
    */
   find(value) {
@@ -102,6 +116,19 @@ class BinarySearchTree {
     return findRecursive(this._root);
   }
 
+  /**
+   * Finds a node by its key
+   * @public
+   * @param {number|string} key
+   * @return {BinarySearchTreeNode}
+   */
+  findKey(key) {
+    if (this._options.key === undefined || this._options.key === null) {
+      throw new Error('Missing key prop name in constructor options');
+    }
+    return this.find({ [this._options.key]: key });
+  }
+
   /**
    * Finds the node with max key (most right) in the tree
    * @public

test/binarySearchTree.test.js

@@ -36,7 +36,7 @@ describe('BinarySearchTree tests', () => {
   });
 
   describe('.has(value)', () => {
-    it('checks if a node exists by key', () => {
+    it('checks if a node exists by value', () => {
       expect(bst.has(50)).to.equal(true);
       expect(bst.has(80)).to.equal(true);
       expect(bst.has(30)).to.equal(true);
@@ -48,8 +48,23 @@ describe('BinarySearchTree tests', () => {
     });
   });
 
+  describe('.has(key)', () => {
+    it('checks if a node exists by key', () => {
+      const testTree = new BinarySearchTree((a, b) => a.id - b.id, { key: 'id' });
+      testTree.insert({ id: 1, name: 'a' });
+      testTree.insert({ id: 2, name: 'b' });
+      testTree.insert({ id: 3, name: 'c' });
+      expect(testTree.has({ id: 1 })).to.equal(true);
+      expect(testTree.has({ id: 2 })).to.equal(true);
+      expect(testTree.has({ id: 3 })).to.equal(true);
+      expect(testTree.hasKey(1)).to.equal(true);
+      expect(testTree.hasKey(2)).to.equal(true);
+      expect(testTree.hasKey(3)).to.equal(true);
+    });
+  });
+
   describe('.find(value)', () => {
-    it('should search a node by its key in the tree', () => {
+    it('should search a node by its value in the tree', () => {
       expect(bst.find(50)).to.be.instanceof(BinarySearchTreeNode);
       expect(bst.find(80)).to.be.instanceof(BinarySearchTreeNode);
       expect(bst.find(30)).to.be.instanceof(BinarySearchTreeNode);
@@ -61,6 +76,21 @@ describe('BinarySearchTree tests', () => {
     });
   });
 
+  describe('.findKey(key)', () => {
+    it('should search a node by its key in the tree', () => {
+      const testTree = new BinarySearchTree((a, b) => a.id - b.id, { key: 'id' });
+      testTree.insert({ id: 1, name: 'a' });
+      testTree.insert({ id: 2, name: 'b' });
+      testTree.insert({ id: 3, name: 'c' });
+      expect(testTree.find({ id: 1 }).getValue()).to.eql({ id: 1, name: 'a' });
+      expect(testTree.find({ id: 2 }).getValue()).to.eql({ id: 2, name: 'b' });
+      expect(testTree.find({ id: 3 }).getValue()).to.eql({ id: 3, name: 'c' });
+      expect(testTree.findKey(1).getValue()).to.eql({ id: 1, name: 'a' });
+      expect(testTree.findKey(2).getValue()).to.eql({ id: 2, name: 'b' });
+      expect(testTree.findKey(3).getValue()).to.eql({ id: 3, name: 'c' });
+    });
+  });
+
   describe('.max()', () => {
     it('get the node with max key', () => {
       const max = bst.max();