Submission #672920

#	Time	Username	Problem	Language	Result	Execution time	Memory
672920		hadnew	Mobile (BOI12_mobile)	C++17	0 / 100	1089 ms	56676 KiB

mobile

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

vector<array<int,2>> points;
int n, l;

auto comp = [](pair<double,double> a, pair<double,double> b){
    return (a.first != b.first) ? a.first < b.first : a.second < b.second;
};

bool test(double r)
{
    vector<pair<double,double>> v;
    
    for (int i = 0; i < n; i++)
    {
        double h = points[i][0]; // x val of center
        double k = points[i][1];
        if (r <= k)
        {
            continue;
        }
        double len = sqrt(pow(r,2)-pow(k,2));
        //cout << "LEG LENGTH: "<<len<<endl;
        pair<double,double> p = make_pair(h-len, h+len);
        v.push_back(p);
    }
    sort(v.begin(), v.end(), comp); 
    /*
    for (auto pii : v)
    {
        cout << pii.first << " - " << pii.second << endl;
    }
    */
    // pairs all sorted
    double ma = -1;
    for (int i = 0; i < v.size(); i++)
    {
        if (v[i].second < v[i+1].first)
        {
            return false;
        }
        ma = max(max(v[i].second,v[i+1].second),ma);
    }
    return v[0].first <= 0 && ma >= l;
}

int main()
{
    cin >> n >> l;
    for (int i = 0; i < n; i++)
    {
        int a, b;
        cin >> a >> b;
        points.push_back(array<int,2>{{a,b}});
    }
    auto comp = [](array<int,2> a, array<int,2> b) {
        return a[0] < b[0];
    };
    sort(points.begin(), points.end(), comp);
    //cout << "ANS: " << ((test(5)) ? "WORKS" : "DOESNT WORK") << endl;
    double lo = 0;
    double hi = 1500000000; // longest r needed is 10e9 sqrt2
    while (lo < hi) // better precision than needed just to be safe
    {
        double mid = lo+(hi-lo)/2;
        if (test(mid))
        {
            hi = mid;
        }
        else
        {
            lo = mid+0.0001;
        }
    }
    cout << lo << endl;
}

Compilation message (stderr)

mobile.cpp: In function 'bool test(double)':
mobile.cpp:37:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<double, double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   37 |     for (int i = 0; i < v.size(); i++)
      |                     ~~^~~~~~~~~~

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