Submission #1346368

#TimeUsernameProblemLanguageResultExecution timeMemory
1346368Jakub_WozniakEvent Hopping (BOI22_events)C++20
0 / 100
1594 ms5852 KiB
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
#define st first
#define nd second
const int maxn = (1e+5)+9;
pair<pii,int> site[maxn];
int kol[maxn];
int res[maxn];
vector <pair<pii,int>> V;
int ojc[maxn];
int jump[maxn] , jumpsiz[maxn];

bool cmp(pair<pii,int> p1 , pair<pii,int> p2)
{
    if(p1.st.nd == p2.st.nd)
    {
        return p1.st.st < p2.st.st;
    }
    return p1.st.nd < p2.st.nd;
}

int main()
{

    int N , Q ,x , y; 
    cin >> N >> Q;
    for(int i = 1 ; i <= N ; i++)
    {
        cin >> site[i].st.st >> site[i].st.nd;
        site[i].nd = i;
    }

    sort(site+1,site+N+1,cmp);
    for(int i = 1 ; i <= N ; i++)
    {
        kol[site[i].nd] = i; 
    }

    for(int i = 0 ; i < Q; i++)
    {
        cin >> x >> y;
        V.push_back({{kol[x],kol[y]},i});
    }

    sort(V.begin() , V.end() , cmp);

    int lst = 0;
    while(lst < N) // O(n*n)
    {
        lst++;
        for(int i = lst-1 ; i >= 1 ; i--)
        {
            if(site[lst].st.st <= site[i].st.nd && site[ojc[i]].st.nd < site[lst].st.nd)
            {
                ojc[i] = lst;
            }
            else if(site[lst].st.st > site[i].st.nd) break;
        }
        ojc[lst] = lst;
    }

    for(int i = N ; i >= 1; i--)
    {
        if(ojc[i] == i)
        {
            jump[i] = i;
            jumpsiz[i] = 1;
            continue;
        }

        if(jumpsiz[ojc[i]] == jumpsiz[jump[ojc[i]]] && jump[ojc[i]] != ojc[i])
        {
            jump[i] = jump[jump[ojc[i]]];
            jumpsiz[i] = jumpsiz[ojc[i]]*2+1;
        }
        else 
        {
            jump[i] = ojc[i];
            jumpsiz[i] = 1;
        }
    }

    
    int ind; pii Z;
    for(auto e : V)
    {
        Z = e.st;
        ind = e.nd;

        if(Z.st == Z.nd)
        {
            res[ind] = 0;
            continue;
        }
        if(site[Z.st].st.nd > site[Z.nd].st.nd)
        {
            res[ind] = maxn*4+5;
            continue;
        }

        int akt = Z.st;
        int resi = 0;
        while(ojc[akt] != akt && site[ojc[akt]].st.nd < site[Z.nd].st.nd) // O(n*Q)
        {
            int J = jump[akt];
            if(ojc[J] != akt && site[ojc[J]].st.nd < site[Z.nd].st.nd)
            {
                resi += jumpsiz[akt];
                akt = J;
                continue;
            }
            resi++;
            akt = ojc[akt];
        }

        
        if(site[Z.nd].st.st <= site[akt].st.nd)
        {
            resi++;
        }
        else resi = maxn*4+5;
        /*
        if(site[Z.nd].st.st <= site[akt].st.nd)
        {
            resi++;
        }
        else
        {
            resi++;
            akt = ojc[akt];
            if(site[Z.nd].st.st <= site[akt].st.nd)
            {
                resi++;
            }
            else resi = maxn*4+5;
        }
        */

        res[ind] = resi;
    }

    for(int i = 0 ; i < Q; i++)
    { 
        if(res[i] == maxn*4+5)cout << "impossible\n";
        else cout << res[i] << '\n';
    }
    return 0;
}


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