Submission #768919

#	Time	Username	Problem	Language	Result	Execution time	Memory
768919		orcslop	Mobile (BOI12_mobile)	C++17	0 / 100	670 ms	48148 KiB

mobile

#include <bits/stdc++.h>
using namespace std;
#define sz(x) (int)(x).size() 

const int MAXN = 1e6; 

int n; 
double l; 
pair<double, double> v[MAXN]; 

bool check(double rad){
    vector<pair<double, double>> intervals(n); 
    for(int i = 0; i < n; i++){
        intervals[i].first = max(v[i].first - sqrt(rad * rad - v[i].second * v[i].second), (double)0); 
        intervals[i].second = min(v[i].first  + sqrt(rad * rad - v[i].second * v[i].second), l); 
    }
    // sort(intervals.begin(), intervals.end()); 
    if(intervals[0].first != 0 || intervals[n-1].second != l) return false; 
    for(int i = 0; i < n-1; i++){
        if(intervals[i].second < intervals[i + 1].first) return false; 
    }
    return true; 
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);
    cin >> n >> l; 
    for(int i = 0; i < n; i++){
        cin >> v[i].first >> v[i].second; 
    }
    // cout << check(5.55); 
    double low = 0, high = (double)2e9; 
    while (low + 0.0001 < high) {
        double mid = low + (high - low) / 2;
        if (check(mid)) high = mid;
        else low = mid;
    }
    cout << setprecision(15) << low << '\n'; 
    return 0; 
}

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