Submission #471406

#	Time	Username	Problem	Language	Result	Execution time	Memory
471406		XII	Mobile (BOI12_mobile)	C++17	100 / 100	611 ms	21912 KiB

mobile

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

using ll = long long;

#define fi first
#define se second
#define mp make_pair
#define eb emplace_back
#define ALL(x) (x).begin(), (x).end()

#define FOR(i, a, b) for(int i = (a); i < (b); ++i)
#define FORU(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)

#define IOS cin.tie(0)->sync_with_stdio(false);
#define PROB "BOI12_mobile"
void Fi(){
    if(fopen(PROB".inp", "r")){
        freopen(PROB".inp", "r", stdin);
        freopen(PROB".out", "w", stdout);
    }
}

double SQ(const double &x){
    return x * x;
}

const ll NONE = -2e18;

ll Round(const double &x){
    return (x * 1000 + 0.5);
}

double firstTrue(double lo, double hi, function<bool(double)> f){
    while(Round(lo) < Round(hi)){
        double mid = lo + (hi - lo) / 2;
        if(f(mid)) hi = mid;
        else lo = mid;
    }
    return hi;
}

int main(){
    IOS;
    Fi();
    int n, l; cin >> n >> l;
    vector<int> x(n), y(n);
    FOR(i, 0, n) cin >> x[i] >> y[i];

    const auto check = [&](const double &r) -> bool{
        double L = NONE, R = NONE;
//        vector<pair<double, double>> range;
        FOR(i, 0, n) if(abs(y[i]) <= r){
            double D = sqrt(SQ(r) - SQ(y[i]));
//            range.eb(x[i] - D, x[i] + D);
            if(L == NONE && R == NONE){
                if(x[i] - D <= 0 && 0 <= x[i] + D){
                    L = x[i] - D;
                    R = x[i] + D;
                }
            } else{
                L = min(L, x[i] - D);
                if(x[i] - D <= R) R = max(R, x[i] + D);
            }
        }
//        sort(ALL(range));
//        double L = range[0].fi, R = range[0].se;
//        FOR(i, 1, range.size()){
//            if(range[i].fi <= R) R = max(R, range[i].se);
//        }
        return (L <= 0 && l <= R);
    };


    cout << fixed << setprecision(3) << firstTrue(0, 3e9, check);

    return 0;
}

Compilation message (stderr)

mobile.cpp: In function 'void Fi()':
mobile.cpp:20:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   20 |         freopen(PROB".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
mobile.cpp:21:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   21 |         freopen(PROB".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 4 / 4
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