<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:
    string hashFn(pair<int, int> state) {
        return to_string(state.first) + "," + to_string(state.second);
    }

    int switchColor(int& color) {
        return 1 - color;
    }

    void fillGraph(int color, vector<vector<int>>& edges, unordered_map<int, vector<vector<int>>>& graph) {
        for(vector<int> edge : edges) {
            int x = edge[0], y = edge[1];

            graph[x][color].push_back(y);
        }
    }

    vector<int> shortestAlternatingPaths(int n, vector<vector<int>>& redEdges, vector<vector<int>>& blueEdges)
    {
        // red = 0, blue = 1

        unordered_map<int, vector<vector<int>>> graph;
        unordered_set<string> seen;
        queue<pair<int, int>> q;
        vector<int> ans(n, -1);

        for(int i = 0; i < n; i++)
            graph[i] = {{}, {}};

        fillGraph(0, redEdges, graph);
        fillGraph(1, blueEdges, graph);
        seen.insert(hashFn({0, 0}));
        q.push({0, 0});
        seen.insert(hashFn({0, 1}));
        q.push({0, 1});

        int distance = 0;
        while(!q.empty()) {
            int currSize = q.size();
            for(int i = 1; i <= currSize; i++) {
                int node = q.front().first, nextColor = switchColor(q.front().second);
                q.pop();
                ans[node] = ans[node] == -1 ? distance : ans[node];

                for(int neighbor : graph[node][nextColor]) {
                    string state = hashFn({neighbor, nextColor});
                    if(seen.find(state) == seen.end()) {
                        seen.insert(state);
                        q.push({neighbor, nextColor});
                    }
                }
            }

            distance++;
        }


        return ans;
    }
};
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