Submission #897873

#	Time	Username	Problem	Language	Result	Execution time	Memory
897873		sofija6	Fence (CEOI08_fence)	C++14	100 / 100	1 ms	468 KiB

fence

#include <bits/stdc++.h>
#define ll long long
#define MAXN 110
using namespace std;
struct point
{
    ll x,y;
};
ll n,m,dist[MAXN];
point h[MAXN],t[MAXN],p0;
bool in[MAXN];
ll Cross(point c,point a,point b)
{
    return (a.x-c.x)*(b.y-c.y)-(a.y-c.y)*(b.x-c.x);
}
bool Cmp(point a,point b)
{
    return Cross(p0,a,b)>0;
}
vector<point> ch;
void Convex_Hull()
{
    ll ind=1;
    for (ll i=2;i<=n;i++)
    {
        if (h[i].y<h[ind].y || (h[i].y==h[ind].y && h[i].x<h[ind].x))
            ind=i;
    }
    swap(h[1],h[ind]);
    p0=h[1];
    sort(h+2,h+1+n,Cmp);
    stack<point> s;
    s.push(h[1]);
    s.push(h[2]);
    s.push(h[3]);
    for (ll i=4;i<=n;i++)
    {
        point a=s.top(),b;
        s.pop();
        b=s.top();
        s.push(a);
        while (Cross(b,a,h[i])<0)
        {
            s.pop();
            a=s.top();
            s.pop();
            b=s.top();
            s.push(a);
        }
        s.push(h[i]);
    }
    while (!s.empty())
    {
        ch.push_back(s.top());
        s.pop();
    }
    reverse(ch.begin(),ch.end());
}
vector<ll> G[MAXN];
int main()
{
    ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    cin >> n >> m;
    for (ll i=1;i<=n;i++)
        cin >> h[i].x >> h[i].y;
    for (ll i=1;i<=m;i++)
        cin >> t[i].x >> t[i].y;
    Convex_Hull();
    ll ans=111*m,cnt=0;
    if (ch.size()<3)
    {
        cout << ans;
        return 0;
    }
    for (ll i=1;i<=m;i++)
    {
        in[i]=true;
        for (ll j=0;j<ch.size();j++)
        {
            point a=ch[j],b=t[i],c=(!j)?ch[ch.size()-1] : ch[j-1];
            in[i]=(in[i] && Cross(c,a,b)>0);
        }
        cnt+=in[i];
    }
    for (ll i=1;i<=n;i++)
    {
        for (ll j=1;j<=n;j++)
        {
            if (i==j)
                continue;
            bool yes=true;
            for (ll l=1;l<=m;l++)
            {
                if (in[l] && Cross(h[i],h[j],t[l])<0)
                {
                    yes=false;
                    break;
                }
            }
            if (yes)
                G[i].push_back(j);
        }
    }
    for (ll i=1;i<=n;i++)
    {
        for (ll j=1;j<=n;j++)
            dist[j]=LLONG_MAX;
        dist[i]=1;
        ll minn=LLONG_MAX;
        queue<ll> q;
        q.push(i);
        while (!q.empty())
        {
            ll t=q.front();
            q.pop();
            for (ll next : G[t])
            {
                if (next==i)
                    minn=min(minn,dist[t]);
                if (dist[t]+1<dist[next])
                {
                    dist[next]=dist[t]+1;
                    q.push(next);
                }
            }
        }
        if (minn!=LLONG_MAX)
            ans=min(ans,(m-cnt)*111+minn*20);
    }
    cout << ans;
    return 0;
}

Compilation message (stderr)

fence.cpp: In function 'int main()':
fence.cpp:78:22: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<point>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   78 |         for (ll j=0;j<ch.size();j++)
      |                     ~^~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10
• Subtask 10: 10 / 10