1
var snakesAndLadders = function (board) {
2
  let n = board.length;
3
  let seen = new Set();
4
  let queue = [[1, 0]];
5

6
  while (queue.length) {
7
    let [label, step] = queue.shift();
8
    //console.log(label, step);
9
    let [r, c] = labelToPosition(label, n);
10
    //console.log(r, c, n);
11
    if (board[r][c] !== -1) {
12
      label = board[r][c];
13
    }
14
    if (label == n * n) {
15
      return step;
16
    }
17
    for (let x = 1; x < 7; x++) {
18
      let nextLabel = label + x;
19
      if (nextLabel <= n * n && !seen.has(nextLabel)) {
20
        seen.add(nextLabel);
21
        queue.push([nextLabel, step + 1]);
22
      }
23
    }
24
  }
25
  return -1;
26
};
27

28
const labelToPosition = (label, n) => {
29
  let row = Math.floor((label - 1) / n);
30
  let col = (label - 1) % n;
31
  //console.log("label", row, col);
32
  if (row % 2 === 0) {
33
    return [n - 1 - row, col];
34
  } else {
35
    return [n - 1 - row, n - 1 - col];
36
  }
37
};