Submission #965070

#	Time	Username	Problem	Language	Result	Execution time	Memory
965070		pcc	Mobile (BOI12_mobile)	C++17	8 / 100	936 ms	57064 KiB

mobile

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

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,popcnt,sse4")

#define ll long long
#define pll pair<ll,ll>
#define pii pair<int,int>
#define fs first
#define sc second
#define tlll tuple<ll,ll,ll>
#define ld double
#define pld pair<ld,ld>

const int mxn = 1e6+10;
ll N,L;
vector<pll> arr;

inline bool check(ld r){
	vector<pld> v;
	for(int i = 0;i<N;i++){
		if(r<arr[i].sc)continue;
		v.push_back(pld(arr[i].fs-sqrt(r*r-arr[i].sc*arr[i].sc),arr[i].fs+sqrt(r*r-arr[i].sc*arr[i].sc)));
		if(v.back().fs<0&&v.back().sc>L)return true;
	}
	//sort(v.begin(),v.end());
	ld pre = 0;
	for(auto &i:v){
		if(pre>L)return true;
		if(pre<i.fs)return false;
		pre = max(pre,i.sc);
	}
	return pre>L;
}

int main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	ld l = 0,r = 1e9*sqrt(2);
	cin>>N>>L;
	for(int i = 0;i<N;i++){
		pll tmp;
		cin>>tmp.fs>>tmp.sc;
		if(i&&tmp.fs == arr.back().fs)arr.back().sc = min(arr.back().sc,tmp.sc);
		else arr.push_back(pll(tmp.fs,abs(tmp.sc)));
	}
	for(int i = 0;r-l>0.001;i++){
		ld mid = (l+r)/2;
		if(check(mid))r = mid;
		else l = mid;
	}
	cout<<fixed<<setprecision(10)<<l<<'\n';
	return 0;
}

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