Add Tower of Hanoi.

Author: trekhleb

src/algorithms/uncategorized/hanoi-tower/__test__/hanoiTower.test.js

@@ -1,42 +1,62 @@
 import hanoiTower from '../hanoiTower';
+import Stack from '../../../../data-structures/stack/Stack';
 
 describe('hanoiTower', () => {
   it('should solve tower of hanoi puzzle with 2 discs', () => {
-    const moveCallbackMock = jest.fn();
+    const moveCallback = jest.fn();
     const numberOfDiscs = 2;
 
-    hanoiTower(numberOfDiscs, moveCallbackMock);
+    const fromPole = new Stack();
+    const withPole = new Stack();
+    const toPole = new Stack();
 
-    expect(moveCallbackMock).toHaveBeenCalledTimes((2 ** numberOfDiscs) - 1);
+    hanoiTower({
+      numberOfDiscs,
+      moveCallback,
+      fromPole,
+      withPole,
+      toPole,
+    });
 
-    expect(moveCallbackMock.mock.calls[0][0]).toBe(1);
-    expect(moveCallbackMock.mock.calls[0][1]).toEqual([1, 2]);
-    expect(moveCallbackMock.mock.calls[0][2]).toEqual([]);
+    expect(moveCallback).toHaveBeenCalledTimes((2 ** numberOfDiscs) - 1);
 
-    expect(moveCallbackMock.mock.calls[1][0]).toBe(2);
-    expect(moveCallbackMock.mock.calls[1][1]).toEqual([2]);
-    expect(moveCallbackMock.mock.calls[1][2]).toEqual([]);
+    expect(fromPole.toArray()).toEqual([]);
+    expect(toPole.toArray()).toEqual([1, 2]);
 
-    expect(moveCallbackMock.mock.calls[2][0]).toBe(1);
-    expect(moveCallbackMock.mock.calls[2][1]).toEqual([1]);
-    expect(moveCallbackMock.mock.calls[2][2]).toEqual([2]);
+    expect(moveCallback.mock.calls[0][0]).toBe(1);
+    expect(moveCallback.mock.calls[0][1]).toEqual([1, 2]);
+    expect(moveCallback.mock.calls[0][2]).toEqual([]);
+
+    expect(moveCallback.mock.calls[1][0]).toBe(2);
+    expect(moveCallback.mock.calls[1][1]).toEqual([2]);
+    expect(moveCallback.mock.calls[1][2]).toEqual([]);
+
+    expect(moveCallback.mock.calls[2][0]).toBe(1);
+    expect(moveCallback.mock.calls[2][1]).toEqual([1]);
+    expect(moveCallback.mock.calls[2][2]).toEqual([2]);
   });
 
   it('should solve tower of hanoi puzzle with 3 discs', () => {
-    const moveCallbackMock = jest.fn();
+    const moveCallback = jest.fn();
     const numberOfDiscs = 3;
 
-    hanoiTower(numberOfDiscs, moveCallbackMock);
+    hanoiTower({
+      numberOfDiscs,
+      moveCallback,
+    });
 
-    expect(moveCallbackMock).toHaveBeenCalledTimes((2 ** numberOfDiscs) - 1);
+    expect(moveCallback).toHaveBeenCalledTimes((2 ** numberOfDiscs) - 1);
   });
 
   it('should solve tower of hanoi puzzle with 6 discs', () => {
-    const moveCallbackMock = jest.fn();
+    const moveCallback = jest.fn();
     const numberOfDiscs = 6;
 
-    hanoiTower(numberOfDiscs, moveCallbackMock);
+    hanoiTower({
+      numberOfDiscs,
+      moveCallback,
+    });
 
-    expect(moveCallbackMock).toHaveBeenCalledTimes((2 ** numberOfDiscs) - 1);
+    expect(moveCallback).toHaveBeenCalledTimes((2 ** numberOfDiscs) - 1);
   });
 });

src/algorithms/uncategorized/hanoi-tower/hanoiTower.js

@@ -1,17 +1,5 @@
 import Stack from '../../../data-structures/stack/Stack';
 
-/**
- * @param {Stack} fromPole
- * @param {Stack} toPole
- * @param {function(disc: number, fromPole: number[], toPole: number[])} moveCallback
- */
-function moveDisc(fromPole, toPole, moveCallback) {
-  moveCallback(fromPole.peek(), fromPole.toArray(), toPole.toArray());
-
-  const disc = fromPole.pop();
-  toPole.push(disc);
-}
-
 /**
  * @param {number} numberOfDiscs
  * @param {Stack} fromPole
@@ -28,7 +16,9 @@ function hanoiTowerRecursive({
 }) {
   if (numberOfDiscs === 1) {
     // Base case with just one disc.
-    moveDisc(fromPole, toPole, moveCallback);
+    moveCallback(fromPole.peek(), fromPole.toArray(), toPole.toArray());
+    const disc = fromPole.pop();
+    toPole.push(disc);
   } else {
     // In case if there are more discs then move them recursively.
 
@@ -64,21 +54,21 @@ function hanoiTowerRecursive({
 /**
  * @param {number} numberOfDiscs
  * @param {function(disc: number, fromPole: number[], toPole: number[])} moveCallback
+ * @param {Stack} [fromPole]
+ * @param {Stack} [withPole]
+ * @param {Stack} [toPole]
  */
-export default function hanoiTower(numberOfDiscs, moveCallback) {
+export default function hanoiTower({
+  numberOfDiscs,
+  moveCallback,
+  fromPole = new Stack(),
+  withPole = new Stack(),
+  toPole = new Stack(),
+}) {
   // Each of three poles of Tower of Hanoi puzzle is represented as a stack
   // that might contain elements (discs). Each disc is represented as a number.
   // Larger discs have bigger number equivalent.
 
-  // The pole from where the discs should be moved.
-  const fromPole = new Stack();
-
-  // The middle pole that should be used as a helper.
-  const withPole = new Stack();
-
-  // The destination pole where all discs need to be moved.
-  const toPole = new Stack();
-
   // Let's create the discs and put them to the fromPole.
   for (let discSize = numberOfDiscs; discSize > 0; discSize -= 1) {
     fromPole.push(discSize);