Submission #417450

#	Time	Username	Problem	Language	Result	Execution time	Memory
417450		jackkkk	Mobile (BOI12_mobile)	C++11	0 / 100	1094 ms	32816 KiB

mobile

#include <bits/stdc++.h>
using namespace std;

int n, l;
vector <pair<double, double>> towers;
vector <pair<double ,double>> intervals;
bool good(double dist){
    intervals.clear();
    //get_intervals
    double mx = 0;
    for(const auto &tower : towers){
        if(tower.second>dist){
            intervals.emplace_back(0, 0);
            continue;
        }
        double range = sqrt((dist*dist)-(tower.second*tower.second));
        intervals.emplace_back(tower.first-range, tower.first+range);
        mx = max(mx, tower.first+range);
        
    }
    sort(intervals.begin(), intervals.end());
    if(intervals[0].first>0 || mx<l){
        return false;
    }
    double curr_max = intervals[0].second;
    
    for(int i = 1; i < (int) intervals.size(); i++){
        if(intervals[i].first>l){
            return true;
        }
        if(curr_max<intervals[i].first){
            return false;
        }
        curr_max=max(curr_max, intervals[i].second);
    }
    return true;
}


int main() {
	// your code goes here
	cin >> n >> l;
	towers.resize(n);
	for(int i = 0; i < n; i++){
	    cin >> towers[i].first >> towers[i].second;
	}
	
	double s = 0, e = DBL_MAX/2, mid;
    while(e-s>0.001){
        mid = (s+e)/2;
        if(good(mid)){
            e=mid;
        }
        else{
            s=mid;
        }
    }
    cout << e << "\n";
    
	
	return 0;
}

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