1
var openLock = function (deadends, target) {
2
  if (deadends.includes("0000")) {
3
    return -1;
4
  }
5
  // treat deadends like visited
6
  // if a number is in visited/deadends, simply ignore it
7
  const visited = new Set(deadends);
8

9
  const queue = [["0000", 0]];
10
  visited.add("0000");
11

12
  while (queue.length) {
13
    const [cur, count] = queue.shift();
14
    if (cur === target) {
15
      return count;
16
    }
17

18
    // each number will create 8 more different paths to check
19

20
    // e.g. if cur = 0000. 8 next/prev numbers to check are
21
    // 1000, 9000, 0100, 0900, 0010, 0090, 0001, 0009
22
    for (let i = 0; i < 4; i++) {
23
      const c = cur[i];
24

25
      let up = Number(c) + 1;
26
      let down = Number(c) - 1;
27
      // if up is 9, then up + 1 = 10 -> set it  to 0
28
      if (up === 10) {
29
        up = "0";
30
      }
31
      // if down is 0. then down - 1 = -1 -> set to 9
32
      if (down === -1) {
33
        down = "9";
34
      }
35

36
      const next = cur.substring(0, i) + up + cur.substring(i + 1);
37
      const prev = cur.substring(0, i) + down + cur.substring(i + 1);
38

39
      // if not visited, push to queue
40
      if (!visited.has(next)) {
41
        visited.add(next);
42
        queue.push([next, count + 1]);
43
      }
44

45
      if (!visited.has(prev)) {
46
        visited.add(prev);
47
        queue.push([prev, count + 1]);
48
      }
49
    }
50
  }
51

52
  return -1;
53
};