Submission #491463

#	Time	Username	Problem	Language	Result	Execution time	Memory
491463		stefantaga	Valley (BOI19_valley)	C++14	100 / 100	250 ms	51012 KiB

valley

#include <bits/stdc++.h>
#define INF 10000000000000000
using namespace std;
typedef long long ll;
ll dist[200005],rmq[200005][20],din[200005][20];
bool viz[200005];
int niv[200005];
vector <pair <int,int>> v[200005];
void dfs(int x,int tata)
{
    if (viz[x]==1)
    {
        din[x][0]=dist[x];
    }
    else
    {
        din[x][0]=INF;
    }
    rmq[x][0]=tata;
    niv[x]=niv[tata]+1;
    for (int i=0;i<v[x].size();i++)
    {
        if (v[x][i].first==tata)
        {
            continue;
        }
        int nod = v[x][i].first;
        dist[nod]=dist[x]+v[x][i].second;
        dfs(nod,x);
        din[x][0]=min(din[x][0],din[nod][0]);
    }
}
struct wow
{
    int x,y,cost;
}muchie[200005];
int s,q,e,i,x,n,lg;
int lca (int x,int y)
{
    if (niv[x]<niv[y])
    {
        return lca(y,x);
    }
    if (x==y)
    {
        return x;
    }
    int dif=niv[x]-niv[y],p=1;
    for (int i=0;i<=lg;i++)
    {
        if ((dif&p))
        {
            x=rmq[x][i];
        }
        p=p*2;
    }
    if (x!=y)
    {
        for (int i=lg;i>=0;i--)
        {
            if (rmq[x][i]!=rmq[y][i])
            {
                x=rmq[x][i];
                y=rmq[y][i];
            }
        }
        x=rmq[x][0];
    }
    return x;
}
int main()
{
    ios_base :: sync_with_stdio(false);
    cin.tie(0);
    #ifdef HOME
    ifstream cin("date.in");
    ofstream cout("date.out");
    #endif // HOME
    cin>>n>>s>>q>>e;
    for (i=1;i<=n-1;i++)
    {
        int x,y,cost;
        cin>>muchie[i].x>>muchie[i].y>>muchie[i].cost;
        x=muchie[i].x;
        y=muchie[i].y;
        cost=muchie[i].cost;
        v[x].push_back({y,cost});
        v[y].push_back({x,cost});
    }
    for (i=1;i<=s;i++)
    {
        cin>>x;
        viz[x]=1;
    }
    dfs(e,0);
    lg=log2(n);
    for (int j=1;j<=n;j++)
    {
        if (din[j][0]==INF)
        {
            continue;
        }
        din[j][0]=din[j][0]-2*dist[j];
    }
    for (i=1;i<=lg;i++)
    {
        for (int j=1;j<=n;j++)
        {
            din[j][i]=min(din[j][i-1],din[rmq[j][i-1]][i-1]);
            rmq[j][i]=rmq[rmq[j][i-1]][i-1];
        }
    }
    for (i=1;i<=q;i++)
    {
        int poz,x,y,ind;
        cin>>ind>>poz;
        x=muchie[ind].x;
        y=muchie[ind].y;
        if (niv[x]<niv[y])
        {
            swap(x,y);
        }
        if (lca(poz,x)!=x)
        {
            cout<<"escaped"<<'\n';
            continue;
        }
        ll minim=din[poz][0];
        int dif=niv[poz]-niv[x]+1;
        int p=1,initialito=poz;
        for (int j=0;j<=lg;j++)
        {
            if ((dif&p))
            {
                minim=min(minim,din[poz][j]);
                poz=rmq[poz][j];
            }
            p=p*2;
        }
        if (minim==INF)
        {
            cout<<"oo"<<'\n';
            continue;
        }
        cout<<minim+dist[initialito]<<'\n';
    }
    return 0;
}

Compilation message (stderr)

valley.cpp: In function 'void dfs(int, int)':
valley.cpp:21:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   21 |     for (int i=0;i<v[x].size();i++)
      |                  ~^~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 41 / 41