Submission #973171

#	Time	Username	Problem	Language	Result	Execution time	Memory
973171		jadai007	Mobile (BOI12_mobile)	C++17	100 / 100	674 ms	48352 KiB

mobile

#include<bits/stdc++.h>

using namespace std;

int n;
double L, x[1000100], y[1000100], l = 0, r = 1e9;
vector<pair<double, double>> vc;

bool solve(double mid){
    vc.clear();
    double ans = 0.0;
    for(int i = 1; i <= n; i++) {
        double dis = sqrt(mid*mid - y[i]*y[i]);
        vc.emplace_back(x[i] - dis, x[i] + dis);
    }
    for(auto x: vc) if(x.first <= ans) ans = max(ans, x.second);
    return ans >= L;
}

int main(){
    cin.tie(nullptr)->sync_with_stdio(false);
    cin >> n >> L;
    for(int i = 1; i<=n; ++i) cin >> x[i] >> y[i];
    while(l + 0.0001 < r){
        double mid = (l + r) / 2;
        if(solve(mid)) r = mid;
        else l = mid + 0.0001;
    }
    cout << fixed << setprecision(6) << l;
}

• Subtask 1: 4 / 4
• Subtask 2: 4 / 4
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• Subtask 21: 5 / 5