Submission #752769

#	Time	Username	Problem	Language	Result	Execution time	Memory
752769		IBory	Seesaw (JOI22_seesaw)	C++14	100 / 100	183 ms	50772 KiB

seesaw

#include <bits/stdc++.h>
#define pii pair<int, int>
typedef long long ll;
using namespace std;

const int MAX = 200007;
ll S[MAX], on[MAX];
vector<pair<double, int>> P;
map<pii, int> check;

double Center(int L, int R) {
	return (S[R] - S[L - 1]) / (double)(R - L + 1);
}

void DFS(int L, int R, double init) {
	if (check.find({ L, R }) != check.end()) return;
	check[{L, R}] = 1;
	P.emplace_back(Center(L, R), R - L + 1);
	if (L == R) return;
	double CL = Center(L, R - 1), CR = Center(L + 1, R);
	if (init <= CR) DFS(L, R - 1, init);
	if (CL <= init) DFS(L + 1, R, init);
}

int main() {
	ios::sync_with_stdio(0); cin.tie(0);
	int N;
	cin >> N;
	for (int i = 1; i <= N; ++i) {
		cin >> S[i];
		S[i] += S[i - 1];
	}

	int g = N / 2;
	double init = S[N] / (double)N;
	DFS(1, N, init);
	sort(P.begin(), P.end());

	double ans = 1e18;
	int cnt = 0, R = 0;
	on[P[0].second] = 1;
	for (int L = 0; L < P.size(); ++L) {
		while (R + 1 < P.size() && cnt != N - 1) {
			int t = P[++R].second;
			if (t != 1 && on[t - 1] && !on[t]) cnt++;
			if (t != N && on[t + 1] && !on[t]) cnt++;
			on[t]++;
		}
		if (cnt == N - 1) ans = min(ans, P[R].first - P[L].first);
		int t = P[L].second;
		on[t]--;
		if (t != 1 && on[t - 1] && !on[t]) cnt--;
		if (t != N && on[t + 1] && !on[t]) cnt--;
	}

	cout.precision(12);
	cout << fixed << ans;
	return 0;
}

Compilation message (stderr)

seesaw.cpp: In function 'int main()':
seesaw.cpp:42:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<double, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |  for (int L = 0; L < P.size(); ++L) {
      |                  ~~^~~~~~~~~~
seesaw.cpp:43:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<double, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   43 |   while (R + 1 < P.size() && cnt != N - 1) {
      |          ~~~~~~^~~~~~~~~~
seesaw.cpp:34:6: warning: unused variable 'g' [-Wunused-variable]
   34 |  int g = N / 2;
      |      ^

• Subtask 1: 1 / 1
• Subtask 2: 33 / 33
• Subtask 3: 33 / 33
• Subtask 4: 33 / 33