Submission #651912

#	Time	Username	Problem	Language	Result	Execution time	Memory
651912		Lobo	Port Facility (JOI17_port_facility)	C++17	22 / 100	17 ms	852 KiB

port_facility

#include<bits/stdc++.h>
using namespace std;
const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()

const int maxn = 2e3+10;
const int mod = 1e9+7;

int n, a[maxn], b[maxn];
pair<int,int> c[maxn];
int ds[maxn], dsl[maxn], dsr[maxn], dsant[maxn];
set<int> dsbs[maxn];
set<pair<pair<int,int>,int>> st; // mp(leftmost,rightmost,index)

int find(int v) {
    if(v == ds[v]) return v;
    return ds[v] = find(ds[v]);
}

void join(int u, int v) {
    if(u == -1 || v == -1) return;
    u = find(u);
    v = find(v);
    if(u == v) return;
    if(st.find(mp(mp(dsl[u],dsr[u]),ds[u])) != st.end()) st.erase(mp(mp(dsl[u],dsr[u]),ds[u]));
    if(st.find(mp(mp(dsl[v],dsr[v]),ds[v])) != st.end()) st.erase(mp(mp(dsl[v],dsr[v]),ds[v]));
    if(dsbs[u].size() < dsbs[v].size()) swap(u,v);
    ds[v] = u;
    dsl[u] = min(dsl[u],dsl[v]);
    dsr[u] = max(dsr[u],dsr[v]);
    for(auto x : dsbs[v]) dsbs[u].insert(x);
    st.insert(mp(mp(dsl[u],dsr[u]),ds[u]));
    join(dsant[u],dsant[v]);
}

void solve() {
    cin >> n;

    for(int i = 1; i <= n; i++) {
        cin >> a[i] >> b[i];
        c[i] = mp(a[i],b[i]);
    }
    sort(c+1,c+1+n);

    for(int i = 1; i <= n; i++) {
        a[i] = c[i].fr;
        b[i] = c[i].sc;
        ds[i] = i;
        dsbs[i].insert(b[i]);
        dsant[i] = -1;
        dsl[i] = b[i];
        dsr[i] = b[i];
    }

    // for(int i = 1; i <= n; i++) {
    //     vector<int> idscomb;
    //     for(int j = 1; j < i; j++) {
    //         if(a[i] < b[j] && b[j] < b[i]) {
    //             join(i,dsant[j]);
    //             join(dsant[i],j);
    //             dsant[i] = j;
    //             dsant[j] = i;
    //         }
    //     }
    // }

    // for(int i = 1; i <= n; i++) {
    //     vector<int> idscomb;
    //     st.insert(mp(mp(b[i],b[i]),i));
    //     for(auto it : st) {
    //         int u = find(it.sc);
    //         bool ok = false;
    //         for(auto x : dsbs[u]) {
    //             if(a[i] < x && x < b[i]) ok = true;
    //         }
    //         if(ok) {
    //             idscomb.pb(u);
    //         }
    //     }

    //     for(auto u : idscomb) {
    //         join(find(i),dsant[find(u)]);
    //         join(dsant[find(i)],find(u));
    //         dsant[find(i)] = find(u);
    //         dsant[find(u)] = find(i);
    //     }
    // }

    set<int> atvs; // the b's of the past ones
    for(int i = 1; i <= n; i++) {
        // cout << st.size() << endl;
        // for(auto x : st) {
        //     cout << x.fr.fr << " " << x.fr.sc << " = " << x.sc << endl;
        // }cout << endl;

        // just be sure that we have someone in (a[i],b[i])
        auto it1 = atvs.upper_bound(a[i]);
        if(it1 == atvs.end() || *it1 > b[i]) {
            st.insert(mp(mp(b[i],b[i]),i));
            atvs.insert(b[i]);
            continue;
        }

        vector<int> idscomb; // ids that I will unite
        auto it = st.upper_bound(mp(mp(b[i],0),0)); // the first interval after b
        // while(it != st.begin() && prev(it)->fr.sc > a[i]) {
        //     it = prev(it);
        //     idscomb.pb(it->sc);
        // }
        for(auto it : st) {
            int u = find(it.sc);
            bool ok = false;
            for(auto x : dsbs[u]) {
                if(a[i] < x && x < b[i]) ok = true;
            }
            if(ok) {
                idscomb.pb(u);
            }
        }

        st.insert(mp(mp(b[i],b[i]),i));
        atvs.insert(b[i]);
        if(idscomb.size()) {
            // combine all this and put i in the dsant of this
            int pivot = idscomb[0];
            for(int i = 1; i < idscomb.size(); i++) {
                join(pivot,idscomb[i]);
            }
            join(dsant[find(pivot)],find(i));
            join(dsant[find(i)],find(pivot));
            dsant[find(i)] = find(pivot);
            dsant[find(pivot)] = find(i);
            // cout << i << " " << pivot << " " << idscomb.size() << endl;
        }
    }

    int ans = 1;
    for(int i = 1; i <= n; i++) {
        if(find(i) == find(dsant[i])) ans = 0;
    }
    for(int i = 1; i <= n; i++) {
        // cout << i << "  --- " << find(i) << endl;
    }
    for(int i = 1; i <= n; i++) {
        join(i,dsant[i]);
        // cout << i << " -> " << dsant[i] << endl;
    }

    for(int i = 1; i <= n; i++) {
        if(find(i) == i) {
            ans*= 2;
            ans%= mod;
        }
    }
    cout << ans << endl;
}

int32_t main() {
    ios::sync_with_stdio(false); cin.tie(0);

    // freopen("in.in", "r", stdin);
    // freopen("out.out", "w", stdout);
    int tt = 1;
    // cin >> tt;
    while(tt--) {
        solve();
    }

}

Compilation message (stderr)

port_facility.cpp: In function 'void solve()':
port_facility.cpp:134:30: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  134 |             for(int i = 1; i < idscomb.size(); i++) {
      |                            ~~^~~~~~~~~~~~~~~~
port_facility.cpp:113:14: warning: variable 'it' set but not used [-Wunused-but-set-variable]
  113 |         auto it = st.upper_bound(mp(mp(b[i],0),0)); // the first interval after b
      |              ^~

• Subtask 1: 10 / 10
• Subtask 2: 12 / 12
• Subtask 3: 0 / 56
• Subtask 4: 0 / 22