Template for Eulerian cycle

- Codechef problem code TOURISTS

Author: coderick14

eulerCycle.cpp

@@ -0,0 +1,65 @@
+//Codechef problem code TOURISTS
+#include <bits/stdc++.h>
+#define ll long long
+#define N 200005
+using namespace std;
+
+set<pair<ll,ll> > edges[N];
+vector<pair<ll,ll> > final_edges(N);
+ll deg[N];
+bool visited[N];
+ll cnt = 0;
+
+void dfs(ll u) {
+	visited[u] = 1;
+	cnt++;
+	set<pair<ll,ll> >::iterator it;
+	for(it = edges[u].begin(); it != edges[u].end(); it++) {
+		if(!visited[it->first])
+			dfs(it->first);
+	}
+}
+
+int main() {
+	ll i,n,e,u,v,index;
+	cin>>n>>e;
+	for(i=0;i<e;i++) {
+		cin>>u>>v;
+		edges[u].insert(make_pair(v,i));
+		edges[v].insert(make_pair(u,i));
+		deg[u] += 1;
+		deg[v] += 1;
+	}
+	for(i=1;i<=n;i++) {
+		if(deg[i] & 1) {
+			cout<<"NO";
+			return 0;
+		}
+	}
+	dfs(1);
+	if(cnt != n) {
+		cout<<"NO";
+		return 0;
+	}
+	cout<<"YES\n";
+	//generate eulerian cycle
+	for(u=1;u<=n;u++) {
+		while(!edges[u].empty()) {
+			ll s = u;
+			do {
+				pair<ll,ll> p = *edges[s].begin();
+				index = p.second;
+				v = p.first;
+				final_edges[index] = make_pair(s,v);
+				edges[s].erase(p);
+				edges[v].erase(make_pair(s,index));
+				s = v;
+			}while(s != u);
+		}
+	}
+	//final_edges store the directed edges in the same order of input
+	for(i=0;i<e;i++) {
+		cout<<final_edges[i].first<<" "<<final_edges[i].second<<"\n";
+	}
+	return 0;
+}