Submission #698215

#	Time	Username	Problem	Language	Result	Execution time	Memory
698215		randmac	Mobile (BOI12_mobile)	C++14	12 / 100	276 ms	8500 KiB

mobile

#include <algorithm>
#include <iostream>
#include <cstdio>
#include <vector>
#include <set>
#include <queue>
#include <math.h>
#include <iomanip>

using namespace std;

// https://oj.uz/problem/view/BOI12_mobile

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    // freopen("mobile.in", "r", stdin);
    // freopen("mobile.out", "w", stdout);

    int N, L;
    cin >> N >> L;

    vector<pair<int, int>> a(N);
    
    for (int i = 0; i < N; i++) {
        cin >> a[i].first >> a[i].second;
    }

    // double ans = -1;
    // for (int i = 0; i < b.size() - 1; i++) {
    //     int x_sum = b[i].first + b[i + 1].first;
    //     int x_diff = b[i + 1].first - b[i].first;

    //     double y_squared = (b[i + 1].second + b[i].second) * (b[i + 1].second - b[i].second);
    //     double x_0 = ( y_squared / x_diff + x_sum) / 2;
    //     double distance = (b[i].first - x_0) * (b[i].first - x_0) + b[i].second * b[i].second;
    //     ans = max(ans, distance);
    // }

    double low = 1, high = 1.5e9;
	while (high - low > 1e-3) {
		double mid = low + (high - low) / 2, curr = 0;
		for (int i = 0; i < N; i++) {
			double delta = sqrt(mid * mid - a[i].second * a[i].second);
			double left = a[i].first - delta, right = a[i].first + delta;
			if (left <= curr) curr = max(curr, right);
		}

		if (curr >= L) high = mid;
		else low = mid;
	}


    // cout << sqrt(ans) << setprecision(4) << endl;
    cout << fixed << setprecision(4) << low << endl;
}

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