제출 #721911

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
721911		drdilyor	Event Hopping (BOI22_events)	C++17	60 / 100	804 ms	99952 KiB

events

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
 
 
const int inf = 1e9 + 1e5;
struct event {
    int l, r, i;
};

struct segtree {
    int n;
    vector<pair<int,int>> t;
    segtree(int n) : n(n), t(n*4, {-1, -1}) {}
    void update(int i, const pair<int,int>& x) {
        t[i+=n] = x;
        for (i /= 2; i >= 1; i/= 2) {
            t[i] = max(t[i*2], t[i*2+1]);
        }
    }
    pair<int,int> query(int l, int r) {
        l += n;
        r += n;
        pair<int,int> res{-1,-1};
        while (l <= r) {
            if (l%2==1) res = max(res, t[l++]);
            if (r%2==0) res = max(res, t[r--]);
            l /= 2;
            r /= 2;
        }
        return res;
    }
};

int subtask_5(int n, int m, int k, vector<event>& ev, vector<event>& og)  {
    segtree mxr(k);

    for (int i = 0; i < n;i ++) {
        mxr.update(ev[i].l, {ev[i].r, i});
    }

    vector jmp(20, vector(n, -1));
    for (int i = 0; i < n; i++) {
        pair<int,int> mx = mxr.query(0, ev[i].r);
        if (mx.first != ev[i].r)
            jmp[0][i] = mx.second;
    }
    for (int j = 1; j < 20; j++)
        for (int i = 0; i < n;i++)
            if (jmp[j-1][i] != -1)
                jmp[j][i] = jmp[j-1][jmp[j-1][i]];

    vector<int> iof(n);
    for (int i = 0; i < n; i++)
        iof[ev[i].i] = i;


    while (m--) {
        int s, e;
        cin >> s >> e;
        s--;e--;
 
        if (s == e) {
            cout << "0\n";
            continue;
        }
        if (og[e].l <= og[s].r && og[s].r <= og[e].r) {
            cout << "1\n";
            continue;
        }
        if (og[e].r < og[s].r) {
            cout << "impossible\n";
            continue;
        }

        int si = iof[s], ei = iof[e];
 
        int res = 0;
        for (int j = 19; j >= 0; j--) {
            if (jmp[j][si] != -1 && ev[jmp[j][si]].r < ev[ei].l) {
                si = jmp[j][si];
                res += 1<<j;
            }
        }
        int j = jmp[0][si];
        if (j != -1 && jmp[0][j] != -1 && ev[ei].l <= ev[jmp[0][j]].r) {
            cout << res+2 << '\n';
        } else {
            cout << "impossible\n";
        }
    }
 
    return 0;
}

int subtask_4(int n, int m, int k, vector<event>& ev, vector<event>& og)  {
 
 
    while (m--) {
        int s, e;
        cin >> s >> e;
        s--;e--;
 
        if (s == e) {
            cout << "0\n";
            continue;
        }
 
 
        int si = 0, ei = 0;
        for (int j = 0; j < n; j++) {
            if (ev[j].i == s) si = j;
            if (ev[j].i == e) ei = j;
        }
 
        int res = 0;
        bool found = 0;
        int left = ev[ei].l;
        set<int> st;
        for (int j = n-1; j >= 0; j--) {
            auto [l,r,_i] = ev[j];
            if (r > ev[ei].r) continue;
            if (r < left) {
                if (st.empty()) break;
                left = *st.begin();
                if (r < left) break;
                st.clear();
                res++;
            }
            if (j == si) {
                res++;
                found = 1;
                break;
            }
            st.insert(l);
            continue;
        }
 
 
        if (found) cout << res << '\n';
        else cout << "impossible\n";
    }
 
    return 0;
}

int subtask_3(int n, int m, int k, vector<event>& ev, vector<event>& og) {
    vector ans(n, vector(n, inf));
    vector<int> mnl(k, inf);
    for (auto [l, r, i] :ev) {
        mnl[r] = min(mnl[r], l);
    }
 
    for (int ei = n-1; ei >= 0; ei--) {
        int res = 0;
        int lb = ev[ei].l, rb = ev[ei].r;
        for (int j = n-1; j >= 0; j--) {
            auto [l,r,_i] = ev[j];
            if (r > ev[ei].r) continue;
            if (r < lb) {
                int mn = inf;
                for (int i = lb; i <= rb; i++)
                    mn = min(mn, mnl[i]);
                lb = mn;
                if (r < lb) break;
                rb = r;
                res++;
            }
            ans[ei][j] = res + 1;
        }
    }
 
    while (m--) {
        int s, e;
        cin >> s >> e;
        s--;e--;
 
        if (s == e) {
            cout << "0\n";
            continue;
        }
 
        int si = 0, ei = 0;
        for (int j = 0; j < n; j++) {
            if (ev[j].i == s) si = j;
            if (ev[j].i == e) ei = j;
        }
 
        if (ans[ei][si] < inf) cout << ans[ei][si] << '\n';
        else cout << "impossible\n";
    }
 
    return 0;
}

int subtask_1(int n, int m, int k, vector<event>& ev, vector<event>& og) {
    vector<int> next(n, -1), dist(n, inf), cc(n, -1);
    for (int i = 1; i < n; i++) {
        if (ev[i-1].l <= ev[i].r)
            next[i-1] = i;
    }
    cc[n-1] = 0;
    for (int i = n-2; i >= 0; i--) {
        if (next[i] !=-1) {
            dist[i] = min(dist[i], 1 + dist[next[i]]);
            cc[i] = cc[i+1];
        }
        else cc[i] = cc[i+1]+1;
    }

    vector<int> iof(n);
    for (int i = 0; i < n; i++)
        iof[ev[i].i] = i;
    while (m--) {
        int s, e;
        cin >> s >> e;
        s--;e--;
        s = iof[s], e = iof[e];
        if (cc[s] != cc[e] || dist[s] < dist[e]) cout << "impossible\n";
        else cout << dist[s] - dist[e] << '\n';
    }
    return 0;
}

int main() {
    int n, m;
    cin >> n >> m;
    vector<event> ev(n), og;
    map<int,int> comp;
    int _i = 0;
    for (auto& [s, e, i] : ev) {
        cin >> s >> e;
        comp[s] = comp[e] = 0;
        i = _i++;
    }
    int k = 0;
    for (auto& mp : comp)
        mp.second = k++;
    for (auto& [s, e, i] : ev)
        s = comp[s], e = comp[e];
 
    og = ev;
    sort(ev.begin(), ev.end(), [&](auto& a, auto& b) {
        return a.r == b.r ? a.l < b.l : a.r < b.r ;
    });

    bool overlap = 0;
    for (int i = 0; i+1 < n;i ++) {
        if (ev[i].l > ev[i+1].l) overlap = 1;
    }
    //for (auto[a,b,c] : ev) cout << a << ' ' << b << ' ' << c <<'\n';
    if (!overlap) return subtask_5(n, m, k, ev, og);
    else if (n <= 5000) return subtask_3(n, m, k, ev, og);
    else if (m <= 100) return subtask_4(n, m, k, ev, og);
    else return subtask_1(n, m, k, ev, og);
}

• Subtask 1: 0 / 10
• Subtask 2: 10 / 10
• Subtask 3: 15 / 15
• Subtask 4: 15 / 15
• Subtask 5: 20 / 20
• Subtask 6: 0 / 30