Submission #1096957

#	Time	Username	Problem	Language	Result	Execution time	Memory
1096957		ocasu	Mobile (BOI12_mobile)	C++17	8 / 100	1064 ms	131072 KiB

mobile

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

#define int long long
#define double long double

double mid(int x1, int y1, int x2, int y2){
    return (double)(x2*x2 - x1*x1 + y2*y2 - y1*y1)/(double)(2*x2-2*x1);
}

double dist(double x1, double y1, double x2, double y2){
    return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}

signed main(){
    int n,l; cin>>n>>l;
    map<int,int> mp;
    for (int i=0; i<n; i++){
        int p,q; cin>>p>>q;
        q=abs(q);
        if (mp.count(p)==0) mp[p]=q;
        mp[p] = min(mp[p], q);
    }
    n=(int)(mp.size());
    vector<int> x, y;
    for (auto [i,j]: mp){
        x.push_back(i), y.push_back(j);
    }
    vector<double> a(n,0), b(n,l);
    

    stack<int> sl;
    //cout<<'\n';
    for (int i=0; i<n; i++){
        double cur = 0;
        while (!sl.empty()) {
            cur = max(cur, mid(x[i],y[i],x[sl.top()],y[sl.top()]));
            if (y[i] >= y[sl.top()]) break;
            sl.pop();
        }
        a[i] = cur;
        //a[i] = min((double)l,a[i]);
        
        //cout<<i<<' '<<cur<<'\n';
        //ans=max(ans, dist(x[i],y[i],cur,0));
        sl.push(i);
    }
    stack<int> sr;
    //cout<<'\n';
    for (int i=n-1; i>=0; i--){
        double cur = l;
        while (!sr.empty()) {
            cur = min(cur, mid(x[i],y[i],x[sr.top()],y[sr.top()]));
            if (y[i] >= y[sr.top()]) break;
            sr.pop();
        }
        b[i] = cur;
        //b[i]=max((double)0, b[i]);

        //cout<<i<<' '<<cur<<'\n';
        //ans=max(ans, dist(x[i],y[i],cur,0));
        sr.push(i);
    }
    double ans=0;

    for (int i=0; i<n; i++){
        if (a[i]<0 or a[i]>l or b[i]<0 or b[i]>l or a[i]>b[i]) continue;
        //a[i] = min((double)l,a[i]);
        //b[i] = max((double)0, b[i]);
        ans=max(ans, dist(x[i],y[i],a[i],0));
        ans=max(ans, dist(x[i],y[i],b[i],0));
    }
    //if (ans>=12 and ans<=12.1){
    //    cout<<l<<'\n';
    //}
    cout << fixed << setprecision(6) << ans << endl;
}

• Subtask 1: 4 / 4
• Subtask 2: 4 / 4
• Subtask 3: 0 / 4
• Subtask 4: 0 / 4
• Subtask 5: 0 / 4
• Subtask 6: 0 / 5
• Subtask 7: 0 / 5
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• Subtask 15: 0 / 5
• Subtask 16: 0 / 5
• Subtask 17: 0 / 5
• Subtask 18: 0 / 5
• Subtask 19: 0 / 5
• Subtask 20: 0 / 5
• Subtask 21: 0 / 5