1
const RED = "red";
2
const BLUE = "blue";
3

4
function mapAllEdges(edges) {
5
  const map = new Map();
6
  for (let edge of edges) {
7
    if (!map.has(edge[0])) {
8
      map.set(edge[0], []);
9
    }
10
    map.get(edge[0]).push(edge[1]);
11
  }
12
  return map;
13
}
14

15
function bfs(color, redNodeMap, blueNodeMap, result) {
16
  const queue = [0];
17
  let length = 0;
18
  let currentColor = color;
19
  while (queue.length > 0) {
20
    const size = queue.length;
21
    for (let i = 0; i < size; i++) {
22
      const node = queue.shift();
23
      if (result[node] === -1 || length < result[node]) {
24
        result[node] = length;
25
      }
26
      const map = RED === currentColor ? redNodeMap : blueNodeMap;
27
      if (map.has(node)) {
28
        const edges = map.get(node);
29
        map.delete(node);
30
        queue.push(...edges);
31
      }
32
    }
33
    length++;
34
    currentColor = RED === currentColor ? BLUE : RED;
35
  }
36
  return result;
37
}
38

39
function shortestPath(redEdges, blueEdges, color, result) {
40
  const redNodeMap = mapAllEdges(redEdges);
41
  const blueNodeMap = mapAllEdges(blueEdges);
42
  bfs(color, redNodeMap, blueNodeMap, result);
43
}
44

45
/**
46
 * @param {number} n
47
 * @param {number[][]} redEdges
48
 * @param {number[][]} blueEdges
49
 * @return {number[]}
50
 */
51
var shortestAlternatingPaths = function (n, redEdges, blueEdges) {
52
  const result = new Array(n).fill(-1);
53
  shortestPath(redEdges, blueEdges, RED, result);
54
  shortestPath(redEdges, blueEdges, BLUE, result);
55
  return result;
56
};