Submission #550794

#	Time	Username	Problem	Language	Result	Execution time	Memory
550794		CyberSleeper	Mobile (BOI12_mobile)	C++14	65 / 100	1093 ms	35844 KiB

mobile

#include <bits/stdc++.h>
#define fastio      ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
#define debug(x)    cout << "Line " << __LINE__ << ", " << #x << " is " << x << endl
#define all(x)      x.begin(), x.end()
#define fi          first
#define se          second
#define mp          make_pair
#define pb          push_back
#define ll          long long
#define ull         unsigned long long
#define pll         pair<ll, ll>
#define pii         pair<int, int>
#define pld         pair<ld, ld>
#define ld          long double
#define nl          endl
#define tb          '\t'
#define sp          ' '
#define sqr(x)      (x)*(x)
#define arr3        array<int, 3>
using namespace std;
 
const int MX=1000005, MOD=1000000007, BLOCK=160, INF=2e9+7, LG=62;
const ll INFF=1000000000000000007;
const ld ERR=1e-3, pi=3.14159265358979323846;

ll N;
ld L;
pld A[MX];

bool valid(ld x){
    ld best=0;
    for(int i=1; i<=N; i++){
        ld dist=sqrt(x*x - A[i].se*A[i].se);
        ld le=A[i].fi-dist, ri=A[i].fi+dist;
        if(le<=best)
            best=max(best, ri);
    }
    return (L<=best);
}

int main(){
    fastio;
    cin >> N >> L;
    for(int i=1; i<=N; i++){
        cin >> A[i].fi >> A[i].se;
    }
    ld le=0, ri=1e10, mi, ans;
    while(le+ERR<=ri){
        mi=(le+ri)/2;
        if(valid(mi)){
            ri=mi;
            ans=mi;
        }else
            le=mi;
    }
    cout << fixed << setprecision(3) << ans << nl;
}

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