Submission #570479

#	Time	Username	Problem	Language	Result	Execution time	Memory
570479		lam	Mobile (BOI12_mobile)	C++17	0 / 100	1094 ms	10632 KiB

mobile

#include <bits/stdc++.h>
#define int long long
#define maxn 100010
using namespace std;
int n,L;
pair<int,int> a[maxn];
typedef long double ld;
bool cmp(pair<ld,ld> x, pair<ld,ld> y)
{
    if (x.second!=y.second) return x.second<y.second;
    return x.first<y.first;
}
bool check(ld val)
{
    vector <pair<ld,ld>> b;
    b.clear();
    for (int i=1; i<=n; i++)
    {
        ld temp=a[i].second;
        temp=1.0*temp*temp;
        if (temp>val) continue;
        temp=val*val-temp;
        temp=1.0*sqrt(temp);
        ld l=a[i].first-temp;
        ld r=a[i].first+temp;
        if (r<0) continue;
        if (l>L) continue;
        b.push_back({l,r});
    }
    ld temp=0.0;
    sort(b.begin(),b.end(),cmp);
    for (int i=0; i<b.size(); i++)
    {
        if (b[i].first<=temp) temp=b[i].second;
    }
    return temp>=L;
}
signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);
    cin>>n>>L;
    for (int i=1; i<=n; i++)
    {
        cin>>a[i].first>>a[i].second;
    }
    ld l=0.0;
    ld r=2*1e9;
    ld ans=-1;
    for (int i=1; i<=100; i++)
    {
        ld mid=l+(r-l)/2;
        if (check(mid))
        {
            ans=mid;
            r=mid;
        }
        else
            l=mid;
    }
    cout<<fixed<<setprecision(3)<<ans;
}

Compilation message (stderr)

mobile.cpp: In function 'bool check(ld)':
mobile.cpp:32:20: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long double, long double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   32 |     for (int i=0; i<b.size(); i++)
      |                   ~^~~~~~~~~

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