Submission #898044

#	Time	Username	Problem	Language	Result	Execution time	Memory
898044		GrindMachine	Event Hopping (BOI22_events)	C++17	100 / 100	111 ms	22612 KiB

events

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) (int)a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x,y) ((x+y-1)/(y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "impossible" << endl

#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)

template<typename T>
void amin(T &a, T b) {
    a = min(a,b);
}

template<typename T>
void amax(T &a, T b) {
    a = max(a,b);
}

#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif

/*

read the edi a long time ago, dont remember much from there except binary lifting

*/

const int MOD = 1e9 + 7;
const int N = 1e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
const int LOG = 17;

template<typename T>
struct segtree {
    // https://codeforces.com/blog/entry/18051

    /*=======================================================*/

    struct data {
        pii a;
    };

    data neutral = {{inf1,inf1}};

    data merge(data &left, data &right) {
        data curr;
        curr.a = min(left.a,right.a);
        return curr;
    }

    void create(int i, T v) {

    }

    void modify(int i, T v) {
        tr[i].a = v;
    }

    /*=======================================================*/

    int n;
    vector<data> tr;

    segtree() {

    }

    segtree(int siz) {
        init(siz);
    }

    void init(int siz) {
        n = siz;
        tr.assign(2 * n, neutral);
    }

    void build(vector<T> &a, int siz) {
        rep(i, siz) create(i + n, a[i]);
        rev(i, n - 1, 1) tr[i] = merge(tr[i << 1], tr[i << 1 | 1]);
    }

    void pupd(int i, T v) {
        modify(i + n, v);
        for (i = (i + n) >> 1; i; i >>= 1) tr[i] = merge(tr[i << 1], tr[i << 1 | 1]);
    }

    data query(int l, int r) {
        data resl = neutral, resr = neutral;

        for (l += n, r += n; l <= r; l >>= 1, r >>= 1) {
            if (l & 1) resl = merge(resl, tr[l++]);
            if (!(r & 1)) resr = merge(tr[r--], resr);
        }

        return merge(resl, resr);
    }
};

void solve(int test_case)
{
    int n,q; cin >> n >> q;
    vector<pii> a(n+5);
    rep1(i,n) cin >> a[i].ff >> a[i].ss;

    auto cmp = [&](array<int,3> ar1, array<int,3> ar2){
        if(ar1[1] != ar2[1]) return ar1[1] < ar2[1];
        return ar1[0] < ar2[0];
    };

    vector<array<int,3>> b(n+5);
    rep1(i,n) b[i] = {a[i].ff,a[i].ss,i};
    sort(b.begin()+1,b.begin()+n+1,cmp);

    rep1(i,n) a[i] = {b[i][0],b[i][1]};

    vector<int> sorted_ind(n+5);
    rep1(i,n) sorted_ind[b[i][2]] = i;

    int up[n+5][LOG], down[n+5][LOG];

    vector<pii> enter(n+5);
    rep1(i,n){
        auto [l,r] = a[i];
        int lo = 1, hi = n;
        int first = -1;

        while(lo <= hi){
            int mid = (lo+hi) >> 1;
            if(l <= a[mid].ss){
                first = mid;
                hi = mid-1;
            }
            else{
                lo = mid+1;
            }
        }

        assert(first != -1);

        pii px = {r,i};
        amax(enter[first],px);
    }

    pii best = {-1,-1};
    int ptr = 1;

    rep1(i,n){
        amax(best,enter[i]);
        up[i][0] = best.ss;
    }

    segtree<pii> st(n+5);
    rep1(i,n) st.pupd(i,{a[i].ff,i});

    rep1(i,n){
        auto [l,r] = a[i];
        int first = -1, last = -1;

        int lo = 1, hi = n;
        while(lo <= hi){
            int mid = (lo+hi) >> 1;
            if(a[mid].ss >= l){
                first = mid;
                hi = mid-1;
            }
            else{
                lo = mid+1;
            }
        }

        lo = 1, hi = n;
        while(lo <= hi){
            int mid = (lo+hi) >> 1;
            if(a[mid].ss <= r){
                last = mid;
                lo = mid+1;
            }
            else{
                hi = mid-1;
            }
        }

        assert(first != -1 and last != -1);
        pii best = st.query(first,last).a;
        down[i][0] = best.ss;
    }

    /*

    rep1(i,n){
        auto [l,r] = a[i];
        pii best = {r,i};
        rep1(j,n){
            if(j == i) conts;
            auto [lx,rx] = a[j];
            if(lx <= r and rx >= r){
                pii px = {rx,j};
                amax(best,px);
            }
        }

        up[i][0] = best.ss;
    }

    rep1(i,n){
        auto [l,r] = a[i];
        pii best = {l,i};
        rep1(j,n){
            if(j == i) conts;
            auto [lx,rx] = a[j];
            if(l <= rx and r >= rx){
                pii px = {lx,j};
                amin(best,px);
            }
        }

        down[i][0] = best.ss;
    }
    
    */

    rep1(j,LOG-1){
        rep1(i,n){
            up[i][j] = up[up[i][j-1]][j-1];
            down[i][j] = down[down[i][j-1]][j-1];
        }
    }

    while(q--){
        int i,j; cin >> i >> j;
        i = sorted_ind[i];
        j = sorted_ind[j];

        if(i == j){
            cout << 0 << endl;
            conts;
        }

        if(a[i].ss > a[j].ss){
            no;
            conts;            
        }

        int ans = 0;

        rev(b,LOG-1,0){
            int p = up[i][b];
            if(a[p].ss < a[j].ss){
                ans += (1<<b);
                i = p;
            }
        }

        rev(b,LOG-1,0){
            int p = down[j][b];
            if(a[p].ff > a[i].ff){
                ans += (1<<b);
                j = p;
            }
        }

        int add = inf1;
        if(a[j].ff <= a[i].ss){
            add = 1;
        }
        else{
            j = down[j][0];
            if(a[i].ss >= a[j].ff and a[i].ss <= a[j].ss){
                add = 2;
            }   
        }

        ans += add;

        if(ans > inf1) no;
        else cout << ans << endl;
    }
}

int main()
{
    fastio;

    int t = 1;
    // cin >> t;

    rep1(i, t) {
        solve(i);
    }

    return 0;
}

Compilation message (stderr)

events.cpp: In function 'void solve(int)':
events.cpp:173:9: warning: unused variable 'ptr' [-Wunused-variable]
  173 |     int ptr = 1;
      |         ^~~

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