Submission #1121047

#	Time	Username	Problem	Language	Result	Execution time	Memory
1121047		Wansur	Event Hopping (BOI22_events)	C++17	100 / 100	233 ms	33104 KiB

events

#include <bits/stdc++.h>
#define f first
#define s second
#define ent '\n'
#define int long long

typedef long long ll;
using namespace std;
const int maxn = 2e5 + 12;
const int mod = 1e9 + 7;

int up[22][maxn];
int l[maxn], r[maxn];
pair<int, int> t[maxn * 4];
int n, m, q;

void upd(int v, int tl, int tr, int pos, pair<int, int> x) {
    if(tl == tr) {
        t[v] = min(t[v], x);
    }
    else {
        int mid = tl + tr >> 1;
        if(pos <= mid) {
            upd(v * 2, tl, mid, pos, x);
        }
        else {
            upd(v * 2 + 1, mid + 1, tr, pos, x);
        }
        t[v] = min(t[v * 2], t[v * 2 + 1]);
    }
}

pair<int, int> get(int v, int tl, int tr, int l, int r) {
    if(tl > r || l > tr) return {1e18, 1e18};
    if(tl >= l && tr <= r) return t[v];
    int mid = tl + tr >> 1;
    return min(get(v * 2, tl, mid, l, r), get(v * 2 + 1, mid + 1, tr, l, r));
}

void solve() {
    cin >> n >> q;
    vector<int> pos;
    for(int i = 1; i <= n; i++) {
        cin >> l[i] >> r[i];
        pos.push_back(l[i]);
        pos.push_back(r[i]);
    }
    sort(pos.begin(), pos.end());
    pos.resize(unique(pos.begin(), pos.end()) - pos.begin());
    m = (int)pos.size();
    for(int i = 1; i <= m * 4; i++) {
        t[i] = {1e18, 1e18};
    }
    for(int i = 1; i <= n; i++) {
        l[i] = lower_bound(pos.begin(), pos.end(), l[i]) - pos.begin();
        r[i] = lower_bound(pos.begin(), pos.end(), r[i]) - pos.begin();
        l[i]++, r[i]++;
        upd(1, 1, m, r[i], {l[i], i});
    }
    for(int i = 1; i <= n; i++) {
        up[0][i] = get(1, 1, m, l[i], r[i]).second;
    }
    for(int k = 1; k < 20; k++) {
        for(int i = 1; i <= n; i++) {
            up[k][i] = up[k - 1][up[k - 1][i]];
        }
    }
    while(q--) {
        int i, j;
        cin >> i >> j;
        if(r[i] > r[j]) {
            cout << "impossible\n";
            continue;
        }
        if(i == j) {
            cout << "0\n";
            continue;
        }
        if(r[i] >= l[j]) {
            cout << "1\n";
            continue;
        }
        int ans = 0;
        for(int k = 19; k >= 0; k--) {
            if(up[k][j] != 0 && l[up[k][j]] > r[i]) {
                j = up[k][j];
                ans += (1 << k);
            }
        }
        ans++;
        j = up[0][j];
        if(i != j) {
            ans++;
        }
        if(l[j] > r[i] || ans > n) {
            cout << "impossible\n";
        }
        else {
            cout << ans << ent;
        }
    }
}

signed main(){

    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t = 1;

//    cin >> t;
    while(t--){
        solve();
    }
}

Compilation message (stderr)

events.cpp: In function 'void upd(long long int, long long int, long long int, long long int, std::pair<long long int, long long int>)':
events.cpp:22:22: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   22 |         int mid = tl + tr >> 1;
      |                   ~~~^~~~
events.cpp: In function 'std::pair<long long int, long long int> get(long long int, long long int, long long int, long long int, long long int)':
events.cpp:36:18: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   36 |     int mid = tl + tr >> 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