Submission #881107

#	Time	Username	Problem	Language	Result	Execution time	Memory
881107		Requiem	Senior Postmen (BOI14_postmen)	C++17	100 / 100	428 ms	82360 KiB

postmen

#include<bits/stdc++.h>
#define int long long
#define pb push_back
#define fast ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#define MOD 1000000007
#define INF 1e18
#define fi first
#define se second
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define FORD(i,a,b) for(int i=a;i>=b;i--)
#define sz(a) ((int)(a).size())
#define endl '\n'
#define pi 3.14159265359
#define TASKNAME "postmen"
template<typename T> bool maximize(T &res, const T &val) { if (res < val){ res = val; return true; }; return false; }
template<typename T> bool minimize(T &res, const T &val) { if (res > val){ res = val; return true; }; return false; }
using namespace std;
typedef pair<int,int> ii;
typedef pair<int,ii> iii;
typedef vector<int> vi;
const int MAXN = 5e5 + 9;
vector<int> g[MAXN];
int n,v,m,deg[MAXN],complexity=0;
bool used[MAXN];
bool solve[MAXN];
ii edge[MAXN];
vector<int> ans;
void dfs(int u){
    while(!g[u].empty()){
        int id = g[u].back();
        g[u].pop_back();
        if (used[id]) continue;
        used[id] = true;
        int v = edge[id].fi + edge[id].se - u;
        dfs(v);
    }
    ans.pb(u);
}
bool inqueue[MAXN];
main()
{
    fast;
    if (fopen(TASKNAME".inp","r")){
        freopen(TASKNAME".inp","r",stdin);
        freopen(TASKNAME".out","w",stdout);
    }
    cin>>n>>m;
    for(int i=1;i<=m;i++){
        int u,v;
        cin>>edge[i].fi>>edge[i].se;
        g[edge[i].fi].pb(i);
        g[edge[i].se].pb(i);
        deg[edge[i].fi]++;
        deg[edge[i].se]++;
    }

    memset(inqueue,false,sizeof(inqueue));
//    for(auto x: ans){
//        cout<<x<<' ';
//    }
//    cout<<endl;

    for(int i=1;i<=n;i++){
        if (deg[i]&1) {
            cout<<"IMPOSSIBLE"<<endl;
            return 0;
        }
    }
    memset(used,false,sizeof(used));
    dfs(1);
    if (ans.size() != m + 1) {
        cout<<"IMPOSSIBLE"<<endl;
        return 0;
    }
    stack<int> st;
    for(auto x: ans){
        if (!inqueue[x]){
            inqueue[x] = true;
            st.push(x);
        }
        else{
            cout<<x<<' ';
            while(!st.empty() and st.top() != x){
                cout<<st.top()<<' ';
                inqueue[st.top()] = false;
                st.pop();
            }
            cout<<endl;
        }
    }
    cout<<endl;
}

Compilation message (stderr)

postmen.cpp:40:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   40 | main()
      | ^~~~
postmen.cpp: In function 'int main()':
postmen.cpp:49:13: warning: unused variable 'u' [-Wunused-variable]
   49 |         int u,v;
      |             ^
postmen.cpp:49:15: warning: unused variable 'v' [-Wunused-variable]
   49 |         int u,v;
      |               ^
postmen.cpp:71:20: warning: comparison of integer expressions of different signedness: 'std::vector<long long int>::size_type' {aka 'long unsigned int'} and 'long long int' [-Wsign-compare]
   71 |     if (ans.size() != m + 1) {
      |         ~~~~~~~~~~~^~~~~~~~
postmen.cpp:44:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   44 |         freopen(TASKNAME".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
postmen.cpp:45:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   45 |         freopen(TASKNAME".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

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