Submission #1259707

#	Time	Username	Problem	Language	Result	Execution time	Memory
1259707		Zbyszek99	Alternating Current (BOI18_alternating)	C++20	0 / 100	3094 ms	27836 KiB

alternating

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace __gnu_pbds;
using namespace std;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;

vector<pii> segs;
int m,n;
vi graph[1001*1001];
bool odw[1001*1001];
int prev_[1001*1001];
int rel_ind[1001];

void dfs(int v, int pop)
{
    prev_[v] = pop;
    odw[v] = 1;
    forall(it,graph[v])
    {
        if(!odw[it]) dfs(it,v);
    }
}

bool ans[1001];

void calc(int s1, int s2)
{
    rep(i,n*2)
    {
        odw[i] = 0;
        prev_[i] = -1;
        graph[i] = {};
    }
    rep(i,n)
    {
        rep(j,n)
        {
            if(i == j) continue;
            int v = i+n*j;
            rep(k,n)
            {
                if(k == i || k == j) continue;
                if((segs[i].ss <= segs[j].ss || segs[j].ss < segs[j].ff) && segs[i].ff <= segs[i].ss && segs[k].ff <= segs[i].ss+1 && (segs[k].ss > segs[i].ss || segs[k].ff > segs[k].ss))
                {
                    graph[v].pb(k+n*j);
                }
                if((segs[i].ss >= segs[j].ss || segs[i].ss < segs[i].ff) && segs[j].ff <= segs[j].ss && segs[k].ff <= segs[j].ss+1 && (segs[k].ss > segs[j].ss || segs[k].ff > segs[k].ss))
                {
                    graph[v].pb(i+n*k);
                }
            }
        }
    }
    dfs(s1+s2*n,-1);
    rep(i,n)
    {
        rep(j,n)
        {
            if(segs[i].ff > segs[i].ss || (segs[i].ss == m && segs[s1].ff == 1))
            if(segs[j].ff > segs[j].ss || (segs[j].ss == m && segs[s2].ff == 1))
            {
            if((segs[i].ss >= segs[s1].ff-1 || (i == s1)) && (segs[j].ss >= segs[s2].ff-1 || j == s2) && odw[i+n*j] && (i != s1 || segs[s1].ff == (segs[s1].ss+1)%n) && (j != s2 || segs[s2].ff == (segs[s2].ss+1)%n) && j != s1 && i != s2)
            {
                vi path;
                int cur = i+n*j;
                ans[rel_ind[s1]] = 0;
                ans[rel_ind[s2]] = 1;
                while(true)
                {
                    if(prev_[cur] == -1 || prev_[cur] == 0) break;
                    ans[rel_ind[cur%n]] = 0;
                    ans[rel_ind[cur/n]] = 1;
                    cur = prev_[cur];
                }
                rep(i,n) cout << ans[i];
                cout << "\n";
                exit(0);
            }
            }
        }
    }
}

int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    //random_start();
    cin >> m >>  n;
    vector<pair<int,pii>> segs2;
    rep(i,n)
    {
        int a,b;
        cin >> a >> b;
        segs2.pb({a,{b,i}});
    }
    sort(all(segs2));
    rep(i,n)
    {
        rel_ind[i] = segs2[i].ss.ss;
        segs.pb({segs2[i].ff,segs2[i].ss.ff});
    }
    calc(0,1);
    if(siz(segs) > 2) calc(0,2);
    if(siz(segs) > 3) calc(0,3);
    if(siz(segs) > 4) calc(0,4);
    
    cout << "impossible\n";
}

• Subtask 1: 0 / 13
• Subtask 2: 0 / 20
• Subtask 3: 0 / 22
• Subtask 4: 0 / 19
• Subtask 5: 0 / 26