Submission #816876

#	Time	Username	Problem	Language	Result	Execution time	Memory
816876		t6twotwo	Parking (CEOI22_parking)	C++17	10 / 100	59 ms	6820 KiB

Main

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define FFOR(i,a,b,c) for(int i=(a);(c)>0?i<=(b):i>=(b);i+=(c))
#define FOOR(i,a,b) FFOR(i,a,(b)-1,1)
#define ROOF(i,a,b) FFOR(i,(b)-1,a,-1)
#define FOR(i,n) FOOR(i,0,n)
#define ROF(i,n) ROOF(i,0,n)
#define FORR(x,v) for(auto &x:v)
#define vc vector
#define sz(v) (int)((v).size())
#define bg begin()
#define en end()
#define em empty()
#define lb lower_bound
#define ub upper_bound
#define pb push_back
#define ppb pop_back()
#define eb emplace_back
#define bk back()
#define fr front()
#define pp pop()
#define all(v) (v).begin(),(v).end()
#define lla(v) (v).rbegin(),(v).rend()
#define f first
#define s second
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int N,M;
    cin>>N>>M;
    vc<int> bot(M),top(M),x(N,-1),y(N),free;
    FOR(i,M){
        cin>>bot[i]>>top[i];
        bot[i]--,top[i]--;
        if(bot[i]!=-1) (x[bot[i]]==-1?x[bot[i]]:y[bot[i]])=i*2;
        if(top[i]!=-1) (x[top[i]]==-1?x[top[i]]:y[top[i]])=i*2+1;
        if(bot[i]==-1&&top[i]==-1) free.pb(i);
    }
    vc<pair<int,int>> ans;
    auto move=[&](int u,int v) {
        ans.eb(u,v);
        int a;
        if(top[u]!=-1){
            a=top[u];
            top[u]=-1;
        }else{
            a=bot[u];
            bot[u]=-1;
        }
        if(bot[v]==-1){
            (x[a]/2==u?x[a]:y[a])=v*2;
            bot[v]=a;
        }else{
            (x[a]/2==u?x[a]:y[a])=v*2+1;
            top[v]=a;
        }
    };
    auto good=[&](int a) {
        return (x[a]%2==1||top[x[a]/2]==-1)&&(y[a]%2==1||top[y[a]/2]==-1);
    };
    vc<bool> parked(N);
    FOR(i,N){
        if(x[i]%2==1&&y[i]%2==1){
            move(x[i]/2,free.bk);
            move(y[i]/2,free.bk);
            free.ppb;
        }
        if(x[i]/2==y[i]/2) parked[i]=1;
    }
    queue<int> q;
    FOR(i,N){
        if(!parked[i]&&good(i)){
            parked[i]=1;
            q.push(i);
        }
    }
    while(!q.em){
        int i=q.fr;q.pp;
        int a=x[i]/2;
        int b=y[i]/2;
        if(top[b]!=-1) swap(a,b);
        move(a,b);
        if(bot[a]!=-1){
            if(!parked[bot[a]]&&good(bot[a])){
                parked[bot[a]]=1;
                q.push(bot[a]);
            }
        }
    }
    FOR(i,N){
        if(!parked[i]){
            cout<<-1;
            return 0;
        }
    }
    cout<<sz(ans)<<"\n";
    for(auto[x,y]:ans){
        cout<<x+1<<" "<<y+1<<"\n";
    }
    return 6/22;
}

• Subtask 1: 0 / 10
• Subtask 2: 10 / 10
• Subtask 3: 0 / 25
• Subtask 4: 0 / 15
• Subtask 5: 0 / 25
• Subtask 6: 0 / 15