Submission #724734

#	Time	Username	Problem	Language	Result	Execution time	Memory
724734		406	Sparklers (JOI17_sparklers)	C++17	100 / 100	78 ms	4404 KiB

sparklers

#include "bits/stdc++.h"
#define int long long
#define dq deque<int>
using namespace std;
const int N = 1.2e5;
int n, k, t, x[N];
dq L, R;
void ps(dq &v) {
	v.push_front(0);
	for (int i = 1; i < v.size(); i++) v[i] += v[i - 1];
}
array<int, 3> find(const dq &v) {
	int mn = v[0];
	for (int i = 1; i < v.size(); i++) {
		mn = min(mn, v[i]);
		if (v[i] >= v[0]) return {v[i], mn, 1};
	}
	return {0, 0, 0};
}
bool solve(array<dq, 2> v) {
	if (v[0][0] + v[1][0] < 0 || v[1].back() + v[0].back() < 0) return false;
	array<int, 3> A[2];
	A[0] = find(v[0]);
	A[1] = find(v[1]);
	while (v[0].size() > 1 || v[1].size() > 1) {
		bool flag = false;
		for (int k = 0; k < 2; k++) if (A[k][2]) {
			if (v[k ^ 1][0] + A[k][1] >= 0) {
				v[k].pop_front();
				while (v[k][0] != A[k][0]) v[k].pop_front();
				A[k] = find(v[k]);
				flag = true;
			}
		}
		if (flag) continue;
		else if (A[0][2] && A[1][2]) return false;
		if (!A[0][2] && !A[1][2]) {
			for (int k = 0; k < 2; k++) reverse(v[k].begin(), v[k].end());
			return solve(v);
		}
		return false;
	}
	return true;
}
bool check(int O) {
	int s = O * 2 * t;
	dq l = L, r = R;
	for (auto &u: l) u = s - u;
	for (auto &u: r) u = s - u;
	ps(l), ps(r);
	return solve(array<dq, 2>{l, r});
}
signed main() {
	ios::sync_with_stdio(0), cin.tie(0);
	cin >> n >> k >> t, k--;
	for (int i = 0; i < n; i++) cin >> x[i];
	for (int i = 0; i < k; i++) L.push_back(x[i + 1] - x[i]);	
	reverse(L.begin(), L.end());
	for (int i = k + 1; i < n; i++) R.push_back(x[i] - x[i - 1]);
	int l = -1, r = 1ll<<35;
	while (r - l > 1) {
		int m = l + r >> 1;
		if (check(m)) r = m;
		else l = m;
	}
	cout << r << '\n';
	/*
	int l = 0;
	for (int i = 35; i >= 0; i--) if (!check(1ll << i | l)) l |= 1 << i;
	cout << (n != 1) * (l + 1);
	*/
}

Compilation message (stderr)

sparklers.cpp: In function 'void ps(std::deque<long long int>&)':
sparklers.cpp:10:20: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::deque<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |  for (int i = 1; i < v.size(); i++) v[i] += v[i - 1];
      |                  ~~^~~~~~~~~~
sparklers.cpp: In function 'std::array<long long int, 3> find(const std::deque<long long int>&)':
sparklers.cpp:14:20: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::deque<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   14 |  for (int i = 1; i < v.size(); i++) {
      |                  ~~^~~~~~~~~~
sparklers.cpp: In function 'int main()':
sparklers.cpp:62:13: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   62 |   int m = l + r >> 1;
      |           ~~^~~

• Subtask 1: 30 / 30
• Subtask 2: 20 / 20
• Subtask 3: 50 / 50