Submission #1233353

#	Time	Username	Problem	Language	Result	Execution time	Memory
1233353		zyadhany	Senior Postmen (BOI14_postmen)	C++20	100 / 100	177 ms	37108 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;
	vector<vp> adj;

	void EulerPath(ll src, int edsz) {
		stack<ll> st;
		st.push(src);
		vi visted(edsz);

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

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

			if (isit) {
				if (ontm[m]) {
					while (ontm[m]) {
						ll tp = tm.top();
						ontm[tp] = 0;
						cout << tp << ' ';
						tm.pop();
					}
					cout << '\n';
				}
				tm.push(m);
				ontm[m] = 1;
				st.pop();
			}
		}		
	}

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

    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, i);
	}
	
	gr.EulerPath(1, m);
}

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: 45 / 45