Add Tower of Hanoi.

Author: trekhleb

src/algorithms/uncategorized/hanoi-tower/README.md

@@ -21,7 +21,7 @@ Animation of an iterative algorithm solving 6-disk problem
 
 With `3` disks, the puzzle can be solved in `7` moves. The minimal 
 number of moves required to solve a Tower of Hanoi puzzle 
-is `2n − 1`, where `n` is the number of disks.
+is `2^n − 1`, where `n` is the number of disks.
 
 ## References
 

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

@@ -3,10 +3,11 @@ import hanoiTower from '../hanoiTower';
 describe('hanoiTower', () => {
   it('should solve tower of hanoi puzzle with 2 discs', () => {
     const moveCallbackMock = jest.fn();
+    const numberOfDiscs = 2;
 
-    hanoiTower(2, moveCallbackMock);
+    hanoiTower(numberOfDiscs, moveCallbackMock);
 
-    expect(moveCallbackMock).toHaveBeenCalledTimes(3);
+    expect(moveCallbackMock).toHaveBeenCalledTimes((2 ** numberOfDiscs) - 1);
 
     expect(moveCallbackMock.mock.calls[0][0]).toBe(1);
     expect(moveCallbackMock.mock.calls[0][1]).toEqual([1, 2]);
@@ -23,17 +24,19 @@ describe('hanoiTower', () => {
 
   it('should solve tower of hanoi puzzle with 3 discs', () => {
     const moveCallbackMock = jest.fn();
+    const numberOfDiscs = 3;
 
-    hanoiTower(3, moveCallbackMock);
+    hanoiTower(numberOfDiscs, moveCallbackMock);
 
-    expect(moveCallbackMock).toHaveBeenCalledTimes(7);
+    expect(moveCallbackMock).toHaveBeenCalledTimes((2 ** numberOfDiscs) - 1);
   });
 
   it('should solve tower of hanoi puzzle with 6 discs', () => {
     const moveCallbackMock = jest.fn();
+    const numberOfDiscs = 6;
 
-    hanoiTower(6, moveCallbackMock);
+    hanoiTower(numberOfDiscs, moveCallbackMock);
 
-    expect(moveCallbackMock).toHaveBeenCalledTimes(63);
+    expect(moveCallbackMock).toHaveBeenCalledTimes((2 ** numberOfDiscs) - 1);
   });
 });