Shortest Path with Alternating Colors
<p>You are given an integer <code>n</code>, the number of nodes in a directed graph where the nodes are labeled from <code>0</code> to <code>n - 1</code>. Each edge is red or blue in this graph, and there could be self-edges and parallel edges.</p>

<p>You are given two arrays <code>redEdges</code> and <code>blueEdges</code> where:</p>

<ul>
	<li><code>redEdges[i] = [a<sub>i</sub>, b<sub>i</sub>]</code> indicates that there is a directed red edge from node <code>a<sub>i</sub></code> to node <code>b<sub>i</sub></code> in the graph, and</li>
	<li><code>blueEdges[j] = [u<sub>j</sub>, v<sub>j</sub>]</code> indicates that there is a directed blue edge from node <code>u<sub>j</sub></code> to node <code>v<sub>j</sub></code> in the graph.</li>
</ul>

<p>Return an array <code>answer</code> of length <code>n</code>, where each <code>answer[x]</code> is the length of the shortest path from node <code>0</code> to node <code>x</code> such that the edge colors alternate along the path, or <code>-1</code> if such a path does not exist.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> n = 3, redEdges = [[0,1],[1,2]], blueEdges = []
<strong>Output:</strong> [0,1,-1]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> n = 3, redEdges = [[0,1]], blueEdges = [[2,1]]
<strong>Output:</strong> [0,1,-1]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= n &lt;= 100</code></li>
	<li><code>0 &lt;= redEdges.length,&nbsp;blueEdges.length &lt;= 400</code></li>
	<li><code>redEdges[i].length == blueEdges[j].length == 2</code></li>
	<li><code>0 &lt;= a<sub>i</sub>, b<sub>i</sub>, u<sub>j</sub>, v<sub>j</sub> &lt; n</code></li>
</ul>
Breadth-First Search; Graph
function shortestAlternatingPaths(
    n: number,
    redEdges: number[][],
    blueEdges: number[][],
): number[] {
    const g: [Graph, Graph] = [{}, {}];
    const ans = Array(n).fill(-1);
    const vis = Array.from({ length: n }, () => Array.from({ length: 2 }, () => false));
    let q: Vertex[] = [
        [0, 0],
        [0, 1],
    ];
    vis[0][0] = vis[0][1] = true;
    let d = 0;
    for (const [i, j] of redEdges) {
        (g[0][i] ??= []).push(j);
    }
    for (const [i, j] of blueEdges) {
        (g[1][i] ??= []).push(j);
    }
    while (q.length) {
        const qNext: Vertex[] = [];
        for (let [i, color] of q) {
            if (ans[i] === -1) {
                ans[i] = d;
            }
            color ^= 1;
            for (const j of g[color][i] ?? []) {
                if (!vis[j][color]) {
                    vis[j][color] = true;
                    qNext.push([j, color as Color]);
                }
            }
        }
        q = qNext;
        d++;
    }
    return ans;
}

type Graph = Record<number, number[]>;
type Color = 0 | 1;
type Vertex = [number, Color];
