<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) {
       vector<int> distr(n,INT_MAX),distb(n,INT_MAX);
       int nn = redEdges.size();
       int mm = blueEdges.size();
       
       vector<int> r[n],b[n],ans(n);
       for(int i=0;i<nn;i++){
        r[redEdges[i][0]].push_back(redEdges[i][1]);
       }

       for(int i=0;i<mm;i++){
        b[blueEdges[i][0]].push_back(blueEdges[i][1]);
       } 

       queue<pair<int,int>> q;
       q.push({0,0});
       q.push({0,1});
       distr[0] = 0,distb[0]=0;
       
       // 0 - r, 1 - b
       while(!q.empty()){
          int clr = q.front().second;
          int nd = q.front().first;

          q.pop();
          
          if(clr == 0){
           for(auto it:b[nd]){
               if(distb[it] > distr[nd] + 1 ){
                distb[it] = distr[nd] + 1;
                q.push({it,1});
               }  
           }
          }

          if(clr == 1){
           for(auto it:r[nd]){
               if(distr[it] > distb[nd] + 1){
                distr[it] = distb[nd] + 1;
                q.push({it,0});
               }  
           }
          }
       }

       for(int i=0;i<n;i++){
        ans[i] = min(distr[i],distb[i]);
        if(ans[i] == INT_MAX) ans[i] = -1;
       }   

       return ans;
    }
};
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