Create Euler Path.cpp

Euler Path.cpp

@@ -0,0 +1,61 @@
+struct DirectedEulerPath
+{
+	int n;
+	vector<vector<int> > g;
+	vector<int> path;
+
+	void init(int _n)
+	{
+		n = _n;
+		g = vector<vector<int> > (n + 1, vector<int> ());
+		path.clear();
+	}
+
+	void add_edge(int u, int v)
+	{
+		g[u].push_back(v);
+	}
+
+	void dfs(int u)
+	{
+		while(g[u].size())
+		{
+			int v = g[u].back();
+			g[u].pop_back();
+			dfs(v);
+		}
+		path.push_back(u);
+	}
+
+	bool getPath()
+	{
+		int ctEdges = 0;
+		vector<int> outDeg, inDeg;
+		outDeg = inDeg = vector<int> (n + 1, 0);
+		for(int i = 1; i <= n; i++)
+		{
+			ctEdges += g[i].size();
+			outDeg[i] += g[i].size();
+			for(auto &u:g[i])
+				inDeg[u]++;
+		}
+		int ctMiddle = 0, src = 1;
+		for(int i = 1; i <= n; i++)
+		{
+			if(abs(inDeg[i] - outDeg[i]) > 1)
+				return 0;
+			if(inDeg[i] == outDeg[i])
+				ctMiddle++;
+			if(outDeg[i] > inDeg[i])
+				src = i;
+		}
+		if(ctMiddle != n && ctMiddle + 2 != n)
+			return 0;
+		dfs(src);
+		reverse(path.begin(), path.end());
+		return (path.size() == ctEdges + 1);
+	}
+};
+
+//Problem 1: https://csacademy.com/contest/round-48/task/matching-substrings/
+//Solution 1: http://p.ip.fi/WTb7