Submission #417582

#	Time	Username	Problem	Language	Result	Execution time	Memory
417582		jackkkk	Mobile (BOI12_mobile)	C++11	8 / 100	1094 ms	48096 KiB

mobile

#include <stdio.h>
#include <iomanip>
#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <map>
#include <array>
#include <deque>
#include <unordered_map>
#include <unordered_set>
#include <set>
#include <algorithm>
#include <stdlib.h>
#include <math.h>
#include <list>
#include <float.h>
#include <climits>
using namespace std;

void quit(){
    cout.flush();
    exit(0);
}

int n, l;
vector <pair<double, double>> towers;
bool good(double dist){
    vector <pair<double ,double>> intervals;
    //get_intervals
    for(const auto &tower : towers){
        if(abs(tower.second)>dist){
            continue;
        }
        double range = sqrt((dist*dist)-(tower.second*tower.second));
        intervals.emplace_back(tower.first-range, tower.first+range);
    }
    sort(intervals.begin(), intervals.end());
	if(intervals.size()==0){
		return false;
	}
    double s = intervals[0].first, f = intervals[0].second;
	intervals.emplace_back(1e50,1e50); //so that it iterates the last one
    for(size_t i = 1; i < intervals.size(); i++){
        if(f<intervals[i].first){
            if(s<=0 && f>=l){
				return true;
			}
			s=intervals[i].first;
			f=intervals[i].second;
        }
		else{
        	f=max(f, intervals[i].second);
		}
    }
    return false;
}
int main() {
	//freopen("qwer.in", "r", stdin);
	//freopen("qwer.out", "w", stdout);
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin >> n >> l;
	towers.resize(n);
	for(int i = 0; i < n; i++){
	    cin >> towers[i].first >> towers[i].second;
	}
	
	double s = 0, e = 1e5, mid;
    while(e-s>0.001){
        mid = (s+e)/2;
        if(good(mid)){
            e=mid;
        }
        else{
            s=mid;
        }
    }
    cout << fixed << setprecision(10) <<e << "\n";
	
	
	quit();
}

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