제출 #720552

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
720552		hail	Mobile (BOI12_mobile)	C++17	100 / 100	706 ms	35400 KiB

mobile

#include <bits/stdc++.h>
 
using namespace std;
 
#define pb push_back
#define fast_io ios::sync_with_stdio(0); cin.tie(0)
#define int long long 
#define pi pair<int, int>
#define mp make_pair
#define ld long double
#define fi first
#define se second
#define db double
 
const int MODa = 7 + (int)1e9;
const int INF = (int)4e18;
const int MOD = 998244353;

int n, l;
const int MXN = 1000005;
int x[MXN]{};
int y[MXN]{};

bool check(db r)
{
    db mx = 0;
    db rr = r*r;
    //cerr<<"r = "<<r<<"\n";
    for(int i=1; i<=n; i++)
    {
        if(r<y[i]) continue;
        db sqv = sqrtl(rr - y[i]*y[i]);
        if(x[i]-sqv>mx) continue;
        mx = max(mx, x[i]+sqv);
        //cerr<<i<<" "<<mx<<"\n";
        if(mx>=l) return true;
    }
    return false;
}

void solve()
{
    cin>>n>>l;
    for(int i=1; i<=n; i++)
    {
        cin>>x[i]>>y[i];
    }

    db high = 6e9;
    db low = 0;
    while(high-low>0.001)
    {
        db mid = (high+low)/2;
        if(check(mid)) high = mid;
        else low = mid;
    }
    cout<<setprecision(30);
    cout<<low<<"\n";
}
 
signed main()
{
    fast_io;
    
    int t=1; 
    //cin>>t;
    while(t--)
    {
        solve();
    }
}

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