1var assert = require('assert');
2
3function wordLadder(begin, end, wordList) {
4  let len = 1;
5  let queue = [begin];
6  const dict = new Set(wordList);
7  const seen = new Set(queue);
8
9  while (queue.length) {
10    const next = [];
11    for (let node of queue) {
12      if (node === end) {
13        return len;
14      }
15
16      const splitNode = node.split('');
17      for (let i = 0; i < splitNode.length; i++) {
18        for (let d = 0; d < 26; d++) {
19          splitNode[i] = String.fromCharCode(97 + d);
20          const nv = splitNode.join('');
21          if (!seen.has(nv) && dict.has(nv)) {
22            next.push(nv);
23            seen.add(nv);
24          }
25          splitNode[i] = node[i];
26        }
27      }
28    }
29    queue = next;
30    len++;
31  }
32
33  return 0;
34}
35
36try {
37  assert.equal(
38    wordLadder('bold', 'hope', [
39      'hope',
40      'hole',
41      'bold',
42      'hold',
43      'cold',
44      'sold',
45      'dold',
46    ]),
47    4
48  );
49
50  console.log(
51    'PASSED: ' +
52      "`wordLadder('bold', 'hope', ['hope', 'hole', 'bold', 'hold', 'cold', 'sold', 'dold'])` should return `4`"
53  );
54} catch (err) {
55  console.log(err);
56}