<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>

class Solution {
   private:
    int bfs(int endNode, int n, unordered_map<int, vector<int>>& redAdjMat, unordered_map<int, vector<int>>& bluAdjMat) {
        vector<int> visitedRed(n, 0), visitedBlue(n, 0);

        queue<pair<int /*node*/, int /*color*/>> bfsQ; /*0->Red, 1->Blu*/
        bfsQ.push({0, 0});
        bfsQ.push({0, 1});
        int distance = 0;

        while (bfsQ.size()) {
            distance++;
            int sz = bfsQ.size();
            for (int i = 0; i < sz; i++) {
                pair<int, int> top = bfsQ.front();
                bfsQ.pop();
                if (!top.second) {
                    for (int i : bluAdjMat[top.first]) {
                        if (i == endNode)
                            return distance;
                        if (!visitedBlue[i]) {
                            visitedBlue[i] = 1;
                            bfsQ.push({i, !top.second});
                        }
                    }
                } else {
                    for (int i : redAdjMat[top.first]) {
                        if (i == endNode)
                            return distance;

                        if (!visitedRed[i]) {
                            visitedRed[i] = 1;
                            bfsQ.push({i, !top.second});
                        }
                    }
                }
            }
        }
        return -1;
    }

   public:
    vector<int> shortestAlternatingPaths(int n, vector<vector<int>>& redEdges, vector<vector<int>>& blueEdges) {
        unordered_map<int, vector<int>> redAdjMat, bluAdjMat;

        for (vector<int>& edg : redEdges) {
            redAdjMat[edg[0]].push_back(edg[1]);
        }
        for (vector<int>& edg : blueEdges) {
            bluAdjMat[edg[0]].push_back(edg[1]);
        }

        vector<int> ans(n, -1);
        ans[0] = 0;

        for (int i = 1; i < n; i++) {
            ans[i] = bfs(i, n, redAdjMat, bluAdjMat);
        }

        return ans;
    }
};
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