2.6 KiB
2.6 KiB
title | id | challengeType | forumTopicId |
---|---|---|---|
Towers of Hanoi | 5951ed8945deab770972ae56 | 5 | 302341 |
Description
towerOfHanoi(4, 'A', 'B', 'C')
. The function should return an array of arrays containing the list of moves, source -> destination.
For example, the array [['A', 'C'], ['B', 'A']]
indicates that the 1st move was to move a disc from stack A to C, and the 2nd move was to move a disc from stack B to A.
Instructions
Tests
tests:
- text: <code>towerOfHanoi</code> is a function.
testString: assert(typeof towerOfHanoi === 'function');
- text: <code>towerOfHanoi(3, ...)</code> should return 7 moves.
testString: assert(res3.length === 7);
- text: <code>towerOfHanoi(3, 'A', 'B', 'C')</code> should return <code>[['A','B'], ['A','C'], ['B','C'], ['A','B'], ['C','A'], ['C','B'], ['A','B']]</code>.
testString: assert.deepEqual(towerOfHanoi(3, 'A', 'B', 'C'), res3Moves);
- text: <code>towerOfHanoi(5, "X", "Y", "Z")</code> 10th move should be Y -> X.
testString: assert.deepEqual(res5[9], ['Y', 'X']);
- text: <code>towerOfHanoi(7, 'A', 'B', 'C')</code> first ten moves are <code>[['A','B'], ['A','C'], ['B','C'], ['A','B'], ['C','A'], ['C','B'], ['A','B'], ['A','C'], ['B','C'], ['B','A']]</code>
testString: assert.deepEqual(towerOfHanoi(7, 'A', 'B', 'C').slice(0, 10), res7First10Moves);
Challenge Seed
function towerOfHanoi(n, a, b, c) {
// Good luck!
return [[]];
}
After Test
const res3 = towerOfHanoi(3, 'A', 'B', 'C');
const res3Moves = [['A', 'B'], ['A', 'C'], ['B', 'C'], ['A', 'B'], ['C', 'A'], ['C', 'B'], ['A', 'B']];
const res5 = towerOfHanoi(5, 'X', 'Y', 'Z');
const res7First10Moves = [['A', 'B'], ['A', 'C'], ['B', 'C'], ['A', 'B'], ['C', 'A'], ['C', 'B'], ['A', 'B'], ['A', 'C'], ['B', 'C'], ['B', 'A']];
Solution
function towerOfHanoi(n, a, b, c) {
const res = [];
towerOfHanoiHelper(n, a, c, b, res);
return res;
}
function towerOfHanoiHelper(n, a, b, c, res) {
if (n > 0) {
towerOfHanoiHelper(n - 1, a, c, b, res);
res.push([a, c]);
towerOfHanoiHelper(n - 1, b, a, c, res);
}
}