Submission #1233312

#	Time	Username	Problem	Language	Result	Execution time	Memory
1233312		zyadhany	Senior Postmen (BOI14_postmen)	C++20	55 / 100	311 ms	327680 KiB

postmen

#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
#include <unordered_map>
#include <unordered_set>

#define ll int
#define ld long double
#define pl pair<ll, ll>
#define vi vector<ll>
#define vii vector<vi>
#define vc vector<char>
#define vcc vector<vc>
#define vp vector<pl>
#define mi map<ll,ll>
#define mc map<char,int>
#define sortx(X) sort(X.begin(),X.end());
#define all(X) X.begin(),X.end()
#define allr(X) X.rbegin(),X.rend()
#define ln '\n'
#define YES {cout << "Alice\n"; return;}
#define NO {cout << "Bob\n"; return;}
#define MUN {cout << "-1\n"; return;}

const int MODE = 1e9 + 7;

using namespace std;

/*
eulerian circuit: that path start and end at the same vertex and visits every edge exactly once.
eulerian path: that path may start and end at different vertices and visits every edge exactly once.

in an undirected graph:
- an eulerian circuit exists if and only if every vertex has even degree and the graph is connected.
- an eulerian path if it's eulerian circuit or if it has exactly two vertices with odd degree and the graph is connected.

in directed graph:
- an eulerian circuit exists if and only if every vertex has equal in-degree and out-degree and the graph is strongly connected.
- an eulerian path exists if it has exactly one vertex with (out-degree - in-degree) = 1, exactly one vertex with (in-degree - out-degree) = 1, and all other vertices have equal indegree and out-degree.

*/
class Graph {
public:
    int size;
	vp Edge;
	vii adj;
	bool isConnected()
	{
		ll summ = 0, n = 0, src = -1;
		vi visited(size + 1);
		stack<int> stack;
		
		for (int i = 0; i < adj.size(); i++)
			if (!adj[i].empty()) n++, src = i;
		if (src != -1) stack.push(src);
		while (!stack.empty())
		{
			int m = stack.top();
			stack.pop();
			if (visited[m]) continue;
			visited[m] = 1, summ++;
			for (auto a : adj[m])
				if (!visited[a]) stack.push(a);
		}	
		return (summ == n);
	}
	
	/* The function returns one of the following values
	0 --> If graph is not Eulerian
	1 --> If graph has an Euler path (Semi-Eulerian)
	2 --> If graph has an Euler Circuit (Eulerian)  */
	int isEulerian()
	{
		if (!isConnected()) return 0;
		int odd = 0;
		for (int i = 0; i <= size; i++)
			odd += (adj[i].size() & 1); 
		if (odd > 2) return 0;
		return (odd)? 1 : 2;
	}

	vii EulerPath(ll src) {
		vii X;

		stack<ll> st;
		st.push(src);
		vector<deque<pl>> Y(size + 1);
		vi visted(Edge.size());

		for (int i = 0; i < Edge.size(); i++)
		{
			int u = Edge[i].first, v = Edge[i].second;
			Y[u].push_back({v, i});
			Y[v].push_back({u, i});			
		}

		stack<ll> tm;
		vi ontm(size + 10);
		while (!st.empty())
		{
			ll m = st.top();
			bool isit = 1;

			while (!Y[m].empty()) {
				pl at = Y[m].front();
				Y[m].pop_front();
				if (visted[at.second]) continue;
				visted[at.second] = 1;
				st.push(at.first);
				isit = 0;
				break;
			}

			if (isit) {
				if (ontm[m]) {
					vi Y;
					while (ontm[m]) {
						ll tp = tm.top();
						ontm[tp] = 0;
						Y.push_back(tp);
						tm.pop();
					}
					X.push_back(Y);
				}
				tm.push(m);
				ontm[m] = 1;
				st.pop();
			}
		}
		
		reverse(all(X));
		return (X);
	}

    void addEdge(int u, int v) {
        adj[u].push_back(v);
        adj[v].push_back(u);
		Edge.push_back({u, v});
	}

    Graph(ll n) {
        size = n;
        adj.resize(n + 1);
    }
};


void solve(int tc) {
	ll n, m;

	cin >> n >> m;

	Graph gr(n+1);
	for (int i = 0; i < m; i++)
	{
		ll u, v; cin >> u >> v;
		gr.addEdge(u, v);
	}
	
	auto res = gr.EulerPath(1);
	for (auto Z : res) {
		for (auto a : Z) cout << a << ' ';
		cout << '\n';
	}
}

int main()
{
    ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
    int size = 1;
    //freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);

    // cin >> size;
    for (int i = 1; i <= size; i++)
        solve(i);
}

• Subtask 1: 38 / 38
• Subtask 2: 17 / 17
• Subtask 3: 0 / 45