<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 {
public:
    vector<int> shortestAlternatingPaths(int n, vector<vector<int>>& redEdges, vector<vector<int>>& blueEdges) {
        unordered_map<int, vector<int>> redGraph, blueGraph;
        for(int i=0;i<redEdges.size();i++)
            redGraph[redEdges[i][0]].push_back(redEdges[i][1]);
        for(int i=0;i<blueEdges.size();i++)
            blueGraph[blueEdges[i][0]].push_back(blueEdges[i][1]);
        vector<int> redDist(n, 2*n), blueDist(n, 2*n);
        redDist[0]=blueDist[0]=0;
        queue<pair<int, int>> q;
        q.push({0, 0});
        q.push({0, 1});
        while(!q.empty())
        {
            int x = q.front().first;
            int c = q.front().second;
            q.pop();
            if(c==0)
            {
                for(auto next:blueGraph[x])
                {
                    if(blueDist[next]>redDist[x]+1)
                    {
                        blueDist[next]=redDist[x]+1;
                        q.push({next, 1});
                    }
                }
            }
            else
            {
                for(auto next:redGraph[x])
                {
                    if(redDist[next]>blueDist[x]+1)
                    {
                        redDist[next]=blueDist[x]+1;
                        q.push({next, 0});
                    }
                }
            }
        }
        vector<int> ans(n, -1);
        for(int i=0;i<n;i++)
        {
            int mini=min(redDist[i], blueDist[i]);
            if(mini!=2*n)
                ans[i]=mini;
        }
        return ans;
    }
};
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