Submission #1312189

#	Time	Username	Problem	Language	Result	Execution time	Memory
1312189		hansen	Mobile (BOI12_mobile)	C++20	4 / 100	1097 ms	65280 KiB

mobile

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define int long long
#define fi first
#define se second
#define test(v)            \
    for (auto &x : (v)) {       \
        cout << x << " ";       \
    }                           \
    cout << "\n";
#define test2d(v) \
    for (int i = 0; i < (int)v.size(); i++) { \
        for (int j = 0; j < (int)v[i].size(); j++) { \
            cout << v[i][j] << " "; \
        } \
        cout << '\n'; \
    }
#define pb push_back
vector<pair<int, int>> dirs = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
mt19937 rng((int)chrono::steady_clock::now().time_since_epoch().count());
int hashp = uniform_int_distribution<int>(10, 1e9)(rng);
int hashm1 = 1e9+7;
int hashm2 = 1e9+9;
int MOD = 1e9 + 7;

bool check(long double dist, vector<array<int, 2>>& a, int len){
    vector<array<long double, 2>> pos;
    for(auto[x, y]: a){
        if (abs(y) > dist) continue;
        long double l = x - sqrt(dist*dist - y*y);
        long double r = x + sqrt(dist*dist - y*y);
        pos.pb({l, r});
    }
    sort(pos.begin(), pos.end(), greater<>());
    while(pos.size() > 1){
        auto[l, r] = pos.back();
        pos.pop_back();
        auto[nl, nr] = pos.back();
        pos.pop_back();
        if(r >= nr){
            pos.pb({l, r});
        } else{
            if(nl > r) return true;
            else pos.pb({l, nr});
        }
    }
    pos[0][0] = max(pos[0][0], (long double)0);
    pos[0][1] = min(pos[0][1], (long double)len);
    return (pos[0][0] != 0 || pos[0][1] != len);
}

void solve(){
    int n, L;
    cin >> n >> L;
    vector<array<int, 2>> a(n);
    for(int i = 0; i < n; i++){
        cin >> a[i][0] >> a[i][1];
    }
    long double l = 0, r = 2e18;
    while(r - l > 1e-3){
        long double m = l + (r-l)/2;
        if(check(m, a, L)) l = m;
        else r = m;
    }
    cout << fixed << setprecision(3) << l;
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    /*
        freopen("feast.in", "r", stdin);
        freopen("feast.out", "w", stdout);
    */
    solve();
    return 0;
}

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