<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>

// red is 0
// blue is 1
class Solution {
public:
    vector<int> shortestAlternatingPaths(int n, vector<vector<int>>& redEdges,
                                         vector<vector<int>>& blueEdges) {
        vector<vector<pair<int, bool>>> adj(n); 

        // Fill the adjacency list
        for (const auto& edge : redEdges) {
            adj[edge[0]].emplace_back(edge[1], 0); // red edge
        }
        for (const auto& edge : blueEdges) {
            adj[edge[0]].emplace_back(edge[1], 1); // blue edge
        }

        vector<int> ans(n, -1);
        vector<vector<bool>> vis(n, vector<bool>(2, false)); // vis[node][color]
        queue<pair<int, int>> q; // (node, last color used)

        q.push({0, -1});
        vis[0][0] = true;
        vis[0][1] =
            true; 
        ans[0] = 0;

        int steps = 0;
        while (!q.empty()) {
            int size = q.size();
            for (int i = 0; i < size; ++i) {
                auto [node, lastColor] = q.front();
                q.pop();

                for (const auto& [neighbor, edgeColor] : adj[node]) {
                    if (edgeColor != lastColor && !vis[neighbor][edgeColor]) {
                        vis[neighbor][edgeColor] = true;
                        if (ans[neighbor] == -1) {
                            ans[neighbor] = steps + 1;
                        }
                        q.push({neighbor, edgeColor});
                    }
                }
            }
            ++steps;
        }

        return ans;
    }
};
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