Submission #1167886

#	Time	Username	Problem	Language	Result	Execution time	Memory
1167886		InvMOD	Mobile (BOI12_mobile)	C++20	100 / 100	508 ms	31680 KiB

mobile

#include<bits/stdc++.h>

using namespace std;

#define fi first
#define se second
#define all(v) (v).begin(), (v).end()
#define compact(v) (v).erase(unique(all(v)), (v).end())

using ld = long double;

void solve()
{
    int n,L; cin >> n >> L;

    vector<pair<ld, ld>> a(n);
    for(int i = 0; i < n; i++){
        cin >> a[i].fi >> a[i].se;
    }

    auto square = [&](ld x) -> ld{
        return x * x;
    };

    // (x - point) ^ 2 + y ^ 2 <= dist ^ 2
    // (new point - x) ^ 2 + y ^ 2 <= dist ^ 2
    // -> new point = sqrt(dist ^ 2 - y ^ 2) + x
    // (0 - y) ^ 2 = - (y ^ 2) wtf im dumb :))

    auto good = [&](ld dist) -> bool{
        ld point = 0;
        for(int i = 0; i < n; i++){
            if(square(a[i].fi - point) + square(a[i].se) <= square(dist)){
                point = max(point, 1.0l * sqrt(square(dist) - square(a[i].se)) + a[i].fi);
            }
        }
        return point >= 1.0l * L;
    };

    ld l = 0, r = 2.0l * L;
    for(int time = 0; time < 64; time++){
        ld mid = (l + r) / 2.0l;
        if(!good(mid)){
            l = mid;
        }
        else r = mid;
    }
    cout << fixed << setprecision(6) << r << "\n";
}

int32_t main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    #define name "InvMOD"
    if(fopen(name".INP", "r")){
        freopen(name".INP", "r", stdin);
        freopen(name".OUT", "w", stdout);
    }

    solve();
    return 0;
}

Compilation message (stderr)

mobile.cpp: In function 'int32_t main()':
mobile.cpp:57:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   57 |         freopen(name".INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
mobile.cpp:58:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   58 |         freopen(name".OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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