Submission #653947

#	Time	Username	Problem	Language	Result	Execution time	Memory
653947		baojiaopisu	Event Hopping (BOI22_events)	C++14	100 / 100	220 ms	17644 KiB

events

#include<bits/stdc++.h>

using namespace std;

using ll = long long;
using ld = long double;
using ull = unsigned long long;

using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;

#define fi first
#define se second
#define pb push_back
#define pf push_front
#define mp make_pair
#define ins insert
#define btpc __builtin_popcount
#define btclz __builtin_clz

#define sz(x) (int)(x.size());
#define all(x) x.begin(), x.end()
#define debug(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int d4x[4] = {1, 0, -1, 0}; int d4y[4] = {0, 1, 0, -1};
int d8x[8] = {0, 1, 1, 1, 0, -1, -1, -1};
int d8y[8] = {1, 1, 0, -1, -1, -1, 0, 1};

template<class X, class Y>
    bool minimize(X &x, const Y &y) {
        if (x > y)
        {
            x = y;
            return true;
        }
        return false;
    }
template<class X, class Y>
    bool maximize(X &x, const Y &y) {
        if (x < y)
        {
            x = y;
            return true;
        }
        return false;
    }

const int MOD = 1e9 + 7; //998244353

template<class X, class Y>
	void add(X &x, const Y &y) {
		x = (x + y);
		if(x >= MOD) x -= MOD;
	}

template<class X, class Y> 
	void sub(X &x, const Y &y) {
		x = (x - y);
		if(x < 0) x += MOD;
	}

/* Author : Le Ngoc Bao Anh, 12A5, LQD High School for Gifted Student*/

const ll INF = 1e9;
const int N = 1e5 + 10;
const int LOG = 16;

int l[N], r[N];
int jump[N][LOG + 2];

struct SegmentTree {
	int n;
	struct NODE {
		int val, pos;

		NODE(int _val = INF, int _pos = INF) : val(_val), pos(_pos) {}
	};

	NODE min(const NODE &a, const NODE &b) {
		return (a.val < b.val ? a : b);
	}

	vector<NODE> node;

	SegmentTree(int _n = 0) {
		n = _n;
		node.resize(4 * n + 7);
		for(int i = 1; i <= 4 * n; i++) node[i] = NODE();
	}

private:
	void Update(NODE c, int pos, int l, int r, int id) {
		node[id] = min(node[id], c);
		if(l == r) return;

		int mid = (l + r) >> 1;
		if(pos <= mid) Update(c, pos, l, mid, id << 1);
		else Update(c, pos, mid + 1, r, id << 1 | 1);
	}

	NODE Get(int l, int r, int lo, int hi, int id) {
		if(l > hi || r < lo) return NODE();
		if(lo <= l && r <= hi) return node[id];

		int mid = (l + r) >> 1;
		return min(Get(l, mid, lo, hi, id << 1), Get(mid + 1, r, lo, hi, id << 1 | 1));
	}
public:
	void update(int val, int p, int pos) {
		Update(NODE(val, p), pos, 1, n, 1);
	}

	int get(int l, int r) {
		NODE ans = Get(1, n, l, r, 1);
		return ans.pos;
	}
};

void solve() {
	int n, q; cin >> n >> q;
	vector<int> val;
	for(int i = 1; i <= n; i++) {
		cin >> l[i] >> r[i];
		val.pb(l[i]); val.pb(r[i]);
	}

	sort(all(val)); val.resize(unique(all(val)) - val.begin());
	SegmentTree IT = SegmentTree(2 * n);
	for(int i = 1; i <= n; i++) {
		l[i] = lower_bound(all(val), l[i]) - val.begin() + 1;
		r[i] = lower_bound(all(val), r[i]) - val.begin() + 1;	
		IT.update(l[i], i, r[i]);
	}

	for(int i = 1; i <= n; i++) {
		int p = IT.get(l[i], r[i]);
		if(l[p] < l[i]) jump[i][0] = p;
	}

	for(int j = 1; j <= LOG; j++) {
		for(int i = 1; i <= n; i++) {
			int u = jump[i][j - 1];
			jump[i][j] = jump[u][j - 1];
		}
	}

	while(q--) {
		int s, e; cin >> s >> e;

		if(s == e) {
			cout << 0 << '\n';
			continue;
		}

		if(r[s] > r[e]) {
			cout << "impossible" << '\n';
			continue;
		}

		if(r[s] >= l[e]) {
			cout << 1 << '\n';
			continue;
		}

		int ans = 0;
		for(int i = LOG; i >= 0; i--) {
			if(!jump[e][i]) continue;
			int id = jump[e][i];
			if(l[id] > r[s]) {
				ans += (1 << i);
				e = id;
			}
		}

		int id = jump[e][0];
		if(id && l[id] <= r[s]) cout << ans + 2 << '\n';
		else cout << "impossible" << '\n';
	}
}

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int tc = 1, ddd = 0;
    // cin >> tc;
    while(tc--) {
        //ddd++;
        //cout << "Case #" << ddd << ": ";
        solve();
    }
}

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:188:17: warning: unused variable 'ddd' [-Wunused-variable]
  188 |     int tc = 1, ddd = 0;
      |                 ^~~

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