<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>> red_table, blue_table, used_red, used_blue;
        for(auto &edge : redEdges){
            red_table[edge[0]].push_back(edge[1]);
            used_red[edge[0]].push_back(0);
        }
        for(auto &edge : blueEdges){
            blue_table[edge[0]].push_back(edge[1]);
            used_blue[edge[0]].push_back(0);
        }

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

        vector<int> cur, colors;
        int depth = 1;

        for(int i = 0; i < red_table[0].size(); ++i){
            cur.push_back(red_table[0][i]);
            colors.push_back(0);
            used_red[0][i] = true;
        }
        for(int i = 0; i < blue_table[0].size(); ++i){
            cur.push_back(blue_table[0][i]);
            colors.push_back(1);
            used_blue[0][i] = true;
        }

        while(cur.size() > 0){
            vector<int> new_cur, new_colors;

            for(int i = 0; i < cur.size(); ++i){
                if(ans[cur[i]] == -1){
                    ans[cur[i]] = depth;
                }
                auto &table = (colors[i]) ? red_table : blue_table;
                auto &used = (colors[i]) ? used_red : used_blue;
                int new_color = (colors[i]) ? 0 : 1;
                auto &vec = table[cur[i]];

                for(int j = 0; j < vec.size(); ++j){
                    // std::cout << i << ' ' << j << std::endl;
                    if(!used[cur[i]][j]){
                        new_cur.push_back(vec[j]);
                        new_colors.push_back(new_color);
                        used[cur[i]][j] = true;
                    }
                }
            }

            cur = new_cur;
            colors = new_colors;
            ++depth;
        }

        return ans;
    }
};
20874