Submission #792946

#	Time	Username	Problem	Language	Result	Execution time	Memory
792946		hugo_pm	Railway Trip (JOI17_railway_trip)	C++17	100 / 100	302 ms	30004 KiB

railway_trip

#include <bits/stdc++.h>
#define int long long
using namespace std;

#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define rep(i, a, b) for(int i = (a); i < (b); i++)
#define sz(v) ((int)((v).size()))

template<typename T>
void chmax(T &x, const T &v) { if (x < v) x = v; }
template<typename T>
void chmin(T &x, const T &v) { if (x > v) x = v; }

using pii = pair<int, int>;
using vi = vector<int>;

string to_string(string s) { return s; }
template <typename T> string to_string(T v) {
	bool first = true;
	string res = "[";
	for (const auto &x : v) {
		if (!first)
			res += ", ";
		first = false;
		res += to_string(x);
	}
	res += "]";
	return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

void dbg_out() { cout << endl; }
template <typename Head, typename... Tail> void dbg_out(Head H, Tail... T) {
	cout << ' ' << to_string(H);
	dbg_out(T...);
}

#ifdef DEBUG
#define dbg(...) cout << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif

const int MAX_N = 1e5, LG = 17;
int level[MAX_N];
int lft[LG][MAX_N], rgt[LG][MAX_N];

pii f(int L, int R, int bit) {
	return make_pair(
		min(lft[bit][L], lft[bit][R]),
		max(rgt[bit][L], rgt[bit][R])
	);
}
signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	int N, K, Q;
	cin >> N >> K >> Q;
	rep(i, 0, N) cin >> level[i];
	lft[0][0] = 0;
	rep(i, 1, N) {
		int j = i-1;
		while (level[j] < level[i]) {
			j = lft[0][j];
		}
		lft[0][i] = j;
	}
	rgt[0][N-1] = N-1;
	for (int i = N-2; i >= 0; --i) {
		int j = i+1;
		while (level[j] < level[i]) {
			j = rgt[0][j];
		}
		rgt[0][i] = j;
	}
	rep(bit, 0, LG-1) {
		rep(i, 0, N) {
			tie(lft[bit+1][i], rgt[bit+1][i]) = f(lft[bit][i], rgt[bit][i], bit);
		}
	}
	rep(iReq, 0, Q) {
		int A, B;
		cin >> A >> B;
		--A, --B;
		if (A > B) swap(A, B);
		int jumps = 0;
		int LA = A, RA = A;
		for (int bit = LG-1; bit >= 0; --bit) {
			auto [newLA, newRA] = f(LA, RA, bit);
			if (newRA < B) {
				tie(LA, RA) = tie(newLA, newRA);
				jumps += (1 << bit);
			}
		}
		int LB = B, RB = B;
		for (int bit = LG-1; bit >= 0; --bit) {
			auto [newLB, newRB] = f(LB, RB, bit);
			if (newLB > RA) {
				tie(LB, RB) = tie(newLB, newRB);
				jumps += (1 << bit);
			}
		}
		if (RA != LB) jumps++;
		cout << jumps - 1 << '\n';
	}
}

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 25 / 25
• Subtask 4: 55 / 55