Submission #655578

#	Time	Username	Problem	Language	Result	Execution time	Memory
655578		bLIC	Mobile (BOI12_mobile)	C++17	0 / 100	1099 ms	81256 KiB

mobile

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

#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)(x).size()
#define ft first
#define sd second
#define pb push_back
#define endl '\n'

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pii> vii;
typedef vector<ll> vl;
typedef pair<ll, ll> pll;
typedef vector<pll> vll;
typedef vector<vi> vvi;

#define dbg if(1)

template <class _T>
string printbit(_T x) {string s="";while(x){s=((x%2)?'1':'0')+s;x/=2;} return s;}
template <class _T>
string printbit(_T x, int len) {string s="";while(len--){s=((x%2)?'1':'0')+s;x/=2;} return s;}

const int MOD = 1e9+7;
const int INF = 1e9;
const int maxN = 1e6+5;


ll n;
long double l;
vector<pair<long double, long double>> cor(maxN);


bool check(long double mid){
     vector<pair<long double, long double>> coord;
     for (int i =0;i<n;i++){
          auto p = cor[i];
          auto power = mid;
          if (p.second-power>0) continue;
          else {
               long double len = sqrt(power*power - p.sd*p.sd);
               coord.pb(make_pair(p.ft-len, p.ft+len));
          }
     }
     // if (coord.empty() || coord[0].ft>1e-5) return false;

     long double curr = 0;
     for (auto x:coord){
          if (x.ft>curr) return false;
          curr = max(curr, x.sd);
          if (curr>=l) return true;
     }
     return curr>=l;
}

void solve(){
     cin>>n>>l;
     for (int i = 0;i<n;i++) {
          cin>>cor[i].ft>>cor[i].sd;
          cor[i].sd = abs(cor[i].sd);
     }
     long double l = 0, r = 1e10;
     while(r-l>1e-5){
          long double mid = (l+r)/2;
          if (check(mid)) r = mid;
          else l = mid;
     }
     cout<<fixed<<setprecision(6)<<r;
}


int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    int t = 1;
//     cin>>t;

    while(t--){

        solve();
        cout<<endl;
    }
}

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