Submission #553412

#	Time	Username	Problem	Language	Result	Execution time	Memory
553412		Hona_Nguyen	Mobile (BOI12_mobile)	C++14	0 / 100	1101 ms	48204 KiB

mobile

#include<bits/stdc++.h>
#define prob "mobile"
#define x first
#define y second
using namespace std;
const int maxn = 1e6;
const int MOD = 1e9 + 7;
const double eps = 1e-9;
int n,L;
pair<double,double> p[maxn+5];
int main(){
//    freopen(prob".inp","r",stdin);
//    freopen(prob".out","w",stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    cin >> n >> L;
    for(int i=1;i<=n;i++) cin >> p[i].x >> p[i].y;
    auto check = [&](double val) -> int{
        vector<pair<double,double>> G;
        for(int i=1;i<=n;i++){
            if(val < p[i].y) return 0;
            double tmp = sqrt(val*val-p[i].y*p[i].y);
            double xL = p[i].x - tmp;
            double xR = p[i].x + tmp;
            G.push_back(make_pair(xL,xR));
        }
        sort(G.begin(),G.end(), [&](const pair<double,double> A, const pair<double,double> B){
             if(A.first == B.first) return A.second < B.second;
             return A.first < B.first;
             });
        double curx = 0;
        for(int i=0;i<n;i++){
            if(G[i].x <= curx){
               curx = max(curx, G[i].y);
            }
        }
        return (curx >= (double)(L));
    };
    double low = 1, high = (double)(2e9), res = 0;
    for(int i=1;i<=100;i++){
        if(high < low) break;
        double mid = (low + high) / (double)(2);
        if(check(mid)){
            res = mid;
            high = mid;
        }
        else{
            low = mid;
        }
    }
    cout << fixed << setprecision(6);
    cout << res;
}

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