Submission #1023076

#	Time	Username	Problem	Language	Result	Execution time	Memory
1023076		tanprodium	Mobile (BOI12_mobile)	C++14	100 / 100	654 ms	51028 KiB

mobile

// include
#include<bits/stdc++.h>

using namespace std;

// define
#define fi    first
#define se    second

#define pub   push_back
#define pob   pop_back
#define puf   push_front
#define pof   pop_front
#define eb    emplace_back
#define upb   upper_bound
#define lwb   lower_bound

#define left  VAN
#define right TAN

#define sz(a)               (int)a.size()
#define all(a)              (a).begin(),(a).end()
#define rall(a)             (a).begin(),(a).end()
#define sort_and_unique(a)  sort(all(a));(a).resize(unique(all(a))-a.begin())
#define max_                max_element
#define min_                min_element

// another define
using ll  = long long;
using ld  = long double;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
using mii = map<int, int>;
using mil = map<int, ll>;
using mli = map<ll, int>;
using mll = map<ll, ll>;
using vi  = vector<int>;
using vl  = vector<ll>;
using vvi = vector<vi>;
using vvl = vector<vl>;

// random
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

// templates
template<class X, class Y>
    bool maximize(X &x, const Y &y) {
        if (y > x) {
            x = y;
            return (true);
        } else return (false);
    }

template<class X, class Y>
    bool minimize(X &x, const Y &y) {
        if (y < x) {
            x = y;
            return (true);
        } else return (false);
    }

template<class T>
    void print(const T &a, const int &l, const int &r) {
        for (int i = l; i <= r; i++)
            cout << a[i] << ' ';
        cout << '\n';
    }

// limit
const int oo = 2e9;
const int N  = 1e6;

// function
void yesno(bool x) {
    cout << (x ? "YES\n" : "NO\n");
}

// mem
ll L;
int n;
ld x[N + 5], y[N + 5];

bool ok(ld d) {
    bool exist = false;
    ld l, r;
    for (int i = 1; i <= n; i++) {
        ld y0 = abs(y[i]);
        if (y0 <= d) {
            ld delta = sqrt(d * d - y0 * y0);
            ld u = x[i] - delta;
            ld v = x[i] + delta;
            if (v >= 0.0) {
                if (!exist) {
                    l = u; r = v;
                    exist = true;
                } else {
                    if (u <= r) {
                        minimize(l, u);
                        maximize(r, v);
                    }
                }
            }
        }
    }
    if (exist && l <= 0.0 && r >= L) return (true);
    else return (false);
}

ld BS() {
    ld l = 0.0, r = 2e9;
    for (int _ = 1; _ <= 42; _++) {
        ld mid = (l + r) / 2;
        if (ok(mid))
            r = mid;
        else l = mid;
    }
    return (r);
}

void solve() {
    cin >> n >> L;
    for (int i = 1; i <= n; i++) {
        cin >> x[i] >> y[i];
    }
    cout << fixed << setprecision(4) << BS() << '\n';
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    int t = 1;
    //cin >> t;

    while (t--) solve();
    return 0;
}

Compilation message (stderr)

mobile.cpp: In function 'bool ok(ld)':
mobile.cpp:107:27: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]
  107 |     if (exist && l <= 0.0 && r >= L) return (true);
      |         ~~~~~~~~~~~~~~~~~~^~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 4 / 4
• Subtask 3: 4 / 4
• Subtask 4: 4 / 4
• Subtask 5: 4 / 4
• Subtask 6: 5 / 5
• Subtask 7: 5 / 5
• Subtask 8: 5 / 5
• Subtask 9: 5 / 5
• Subtask 10: 5 / 5
• Subtask 11: 5 / 5
• Subtask 12: 5 / 5
• Subtask 13: 5 / 5
• Subtask 14: 5 / 5
• Subtask 15: 5 / 5
• Subtask 16: 5 / 5
• Subtask 17: 5 / 5
• Subtask 18: 5 / 5
• Subtask 19: 5 / 5
• Subtask 20: 5 / 5
• Subtask 21: 5 / 5