Submission #1259904

#	Time	Username	Problem	Language	Result	Execution time	Memory
1259904		ewirlan	Alternating Current (BOI18_alternating)	C++20	19 / 100	116 ms	15428 KiB

alternating

//
#ifndef __SIZEOF_INT128__
  #define __SIZEOF_INT128__
#endif
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace chrono;
using namespace __gnu_pbds;
template <typename T> using oset =  tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define rep(i, p, k) for(int i(p); i < (k); ++i)
#define per(i, p, k) for(int i(p); i > (k); --i)
#define sz(x) (int)(x).size()
#define sc static_cast
typedef long long ll;
typedef long double ld;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef __int128_t lll;
//#define int ll
template <typename T = int> using par = std::pair <T, T>;
#define fi first
#define se second
#define test int _number_of_tests(in()); while(_number_of_tests--)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define pb emplace_back
struct Timer {
    string name{""};
    time_point<high_resolution_clock> end, start{high_resolution_clock::now()};
    duration<float, std::milli> dur;
    Timer() = default;
    Timer(string nm): name(nm) {}
    ~Timer() {
        end = high_resolution_clock::now(); dur= end - start;
        cout << "@" << name << "> " << dur.count() << " ms" << '\n';
    }
};
template <typename T = int> inline T in()
{
    static T x;
    std::cin >> x;
    return x;
}
std::string yn(bool b)
{
    if(b) return "YES\n";
    else return "NO\n";
}
template <typename F, typename S> std::ostream& operator<<(std::ostream& out, const std::pair <F, S>& par);
template <typename T> std::ostream& operator<< (std::ostream& out, const std::vector <T>& wek)
{
    for(const auto& i : wek)out << i << ' ';
    return out;
}
template <typename F, typename S> std::ostream& operator<<(std::ostream& out, const std::pair <F, S>& par)
{
    out << '{'<<par.first<<", "<<par.second<<"}";
    return out;
}
#define show(x) cerr << #x << " = " << x << '\n';
constexpr int maxn = 1e5 + 3, pol = 1<<17, tres = pol*2+3;
vector <int> la[maxn], lb[maxn];
int tr[2][tres], tr2[2][tres];
void upd(int k, int w){
    tr[k][w*2] += tr2[k][w];
    tr2[k][w*2] += tr2[k][w];
    tr[k][w*2+1] += tr2[k][w];
    tr2[k][w*2+1] += tr2[k][w];
    tr2[k][w] = 0;
}
void addb(int K, int a, int b, int c, int p, int k, int w)
{
    if(a > k || p > b)return;
    if(a <= p && k <= b){
        tr[K][w] += c;
        tr2[K][w] += c;
        return;
    }
    upd(K, w);
    addb(K, a, b, c, p, (p+k)/2, w*2);
    addb(K, a, b, c, (p+k)/2+1, k, w*2+1);
    tr[K][w] = min(tr[K][w*2], tr[K][w*2+1]);
}
int n;
void add(int k, int a, int b, int c){
    if(a <= b) addb(k, a, b, c, 1, pol, 1);
    else{
        add(k, a, n, c);
        add(k, 1, b, c);
    }
}
int minb(int K, int a, int b, int p, int k, int w)
{
    if(a > k || p > b)return 1e9;
    if(a <= p && k <= b)return tr[K][w];
    upd(K, w);
    return min(minb(K, a, b, p, (p+k)/2, w*2), minb(K, a, b, (p+k)/2+1, k, w*2+1));
}
int sum(int k, int a, int b){
    if(a <= b)return minb(k, a, b, 1, pol, 1);
    else return min(sum(k, a, n), sum(k, 1, b));
}
std::int32_t main()
{
    std::cout.tie(nullptr); //for luck
    std::cin.tie(nullptr); std::ios_base::sync_with_stdio(0);
    cin >> n;
    int m(in());
    vector <int> o(m);
    vector <int> a(m), b(m);
    rep(i, 0, m){
        cin >> a[i] >> b[i];
        la[a[i]].pb(i);
        lb[b[i]].pb(i);
    }
    rep(i, 1, n+1)sort(all(la[i]), [&](int x, int y){
        int xb(b[x]), yb(b[y]);
        if(xb < i)xb += n;
        if(yb < i)yb += n;
        return xb > yb;
    });
    set <pair <int, int>> S;
    rep(i, 0, m)if(a[i] > b[i])S.insert({b[i],i});
    vector <int> g(m, -1);
    rep(i, 1, n+1){
        for(auto j: la[i]){
            if(sz(S) && b[j]+n*(b[j]<a[j]) <= S.rbegin()->first) g[j] = S.rbegin()->second;
            else S.insert({b[j]+n*(b[j]<a[j]), j});
        }
        for(auto j: lb[i])S.erase({i,j});
    }
    vector <int> v;
    rep(i, 0, m){
        if(g[i] == -1) v.pb(i);
        else{
            add(0, a[i], b[i], 1);
            add(1, a[i], b[i], 1);
        }
    }
    sort(all(v), [&](int x, int y){return a[x] < a[y];});
    if(sz(v) % 2 == 0){
        rep(i, 0, sz(v))add(i%2, a[v[i]], b[v[i]], 1);
        if(sum(0, 1, n) == 0 || sum(1, 1, n) == 0){
            cout << "impossible\n";
            return 0;
        }
        else{
            vector <bool> o(m);
            rep(i, 0, sz(v))o[v[i]] = i%2;
            rep(i, 0, m)if(g[i] != -1)o[i] = !o[g[i]];
            rep(i, 0, m)cout << o[i];
            cout << '\n';
            return 0;
        }
    }
    else{
        rep(i, 0, sz(v)) add(i%2, a[v[i]], b[v[i]], 1);
        vector <bool> o(m);
        rep(i, 0, sz(v))o[v[i]] = i%2;
        int z(0);
        while(z < sz(v) && (sum(0, 1, n) == 0 || sum(1, 1, n) == 0)){
            add(z%2, a[v[z]], b[v[z]], -1);
            add(!(z%2), a[v[z]], b[v[z]], 1);
            o[z] = !o[z];
            // rep(i, 0, sz(v))cout << o[v[i]];
            // cout << '\n';
            // cout << sum(0, 1, n) << ' ' << sum(1, 1, n) << '\n';
            ++z;
        }
        if(z == sz(v)){
            cout << "impossible\n";
            return 0;
        }
        else{
            rep(i, 0, m)if(g[i] != -1)o[i] = !o[g[i]];
            rep(i, 0, m)cout << o[i];
            cout << '\n';
            return 0;
        }
    }
    return 0;
}

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