Submission #599863

#	Time	Username	Problem	Language	Result	Execution time	Memory
599863		JooDdae	Event Hopping (BOI22_events)	C++17	30 / 100	118 ms	19156 KiB

events

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int n, q, sp[100100][20], mn[100100][20], R[100100], rev[100100];
array<int, 3> a[100100];

int find(int a, int b){
    int k = 31 - __builtin_clz(b - a);
    return min(mn[a][k], mn[b-(1<<k)+1][k]);
}

int main(){
    cin.tie(0)->sync_with_stdio(0);
    cin >> n >> q;
    for(int i=1;i<=n;i++) cin >> a[i][1] >> a[i][0], a[i][2] = i;
    sort(a+1, a+1+n);

    for(int i=n;i>=1;i--){
        auto [e, s, id] = a[i];

        R[i] = a[i+1][0] == e ? R[i+1] : i;
        rev[id] = i;
        mn[i][0] = lower_bound(a+1, a+1+n, array<int, 3>({s, 0, 0})) - a;
    }

    for(int j=1;j<20;j++) for(int i=1;i<=n;i++) if(i+(1<<j)-1 <= n) mn[i][j] = min(mn[i][j-1], mn[i+(1<<j-1)][j-1]);

    for(int i=1;i<=n;i++) sp[i][0] = find(i, R[i]);
    for(int j=1;j<20;j++) for(int i=1;i<=n;i++) sp[i][j] = min(sp[i][j-1], sp[sp[i][j-1]][j-1]);


    while(q--){
        int a, b; cin >> a >> b;
        a = rev[a], b = rev[b];

        if(R[b] < a) {
            cout << "impossible\n";
        } else if(a == b) {
            cout << "0\n";
        } else {
            int ans = 0;

            for(int i=19;i>=0;i--) if(sp[b][i] > a) b = sp[b][i], ans += 1 << i;
            ans++, b = sp[b][0];

            if(a < b) cout << "impossible\n";
            else cout << ans << "\n";
        }
    }
}

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:27:106: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
   27 |     for(int j=1;j<20;j++) for(int i=1;i<=n;i++) if(i+(1<<j)-1 <= n) mn[i][j] = min(mn[i][j-1], mn[i+(1<<j-1)][j-1]);
      |                                                                                                         ~^~

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