Submission #1005136

#	Time	Username	Problem	Language	Result	Execution time	Memory
1005136		vjudge1	Railway (BOI17_railway)	C++17	100 / 100	55 ms	40644 KiB

railway

#pragma GCC optimize("-O3")
#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define vl vector<ll>
#define vi vector<int>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define pb push_back
#define p_b pop_back
#define f first
#define s second
using namespace std;
using namespace __gnu_pbds;
typedef tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
const ll sz = 1e5+5;
vl g[sz];
ll vis[sz], lev[sz], intime[sz], p[30][sz], dist[sz], tin = 1;
void dfs(ll node)
{
    vis[node] = 1;
    intime[node] = tin++;
    for(auto u : g[node])
    {
        if(vis[u])
            continue;
        lev[u] = lev[node] + 1;
        p[0][u] = node;
        dfs(u);
    }
}
ll jump(ll x, ll k)
{
    for(ll i = 0; i < 27; i++)
    {
        if((k >> i) & 1)
            x = p[i][x];
    }
    return x;
}
ll lca(ll x, ll y)
{
    if(lev[x] > lev[y])
        swap(x, y);
    ll d = lev[y] - lev[x];
    y = jump(y, d);
    if(x == y)
        return x;
    else
    {
        for(ll i = 26; i >= 0; i--)
        {
            if(p[i][x] != p[i][y])
            {
                x = p[i][x];
                y = p[i][y];
            }
        }
        return p[0][x];
    }
}
void dfs2(ll node)
{
    vis[node] = 1;
    for(auto u : g[node])
    {
        if(vis[u])
            continue;
        dfs2(u);
        dist[node] += dist[u];
    }
}
void solve()
{
    ll n, m, k, i, j;
    cin >> n >> m >> k;
    vector<pll>edges;
    for(i = 1; i <= n - 1; i++)
    {
        ll x, y;
        cin >> x >> y;
        edges.pb({x, y});
        g[x].pb(y);
        g[y].pb(x);
    }
    dfs(1);
    for(i = 1; i < 27; i++)
    {
        for(j = 1; j <= n; j++)
            p[i][j] = p[i-1][p[i-1][j]];
    }
    for(i = 1; i <= m; i++)
    {
        ll s;
        cin >> s;
        vector<pll>vect;
        for(j = 1; j <= s; j++)
        {
            ll x;
            cin >> x;
            vect.pb({intime[x], x});
        }
        sort(all(vect));
        vect.pb({vect[0].f, vect[0].s});
        for(j = 0; j < s; j++)
        {
            ll x = vect[j].s, y = vect[j+1].s;
            ll a = lca(x, y);
            dist[x]++;
            dist[y]++;
            dist[a] -= 2;
        }
    }
    for(i = 1; i <= n; i++)
        vis[i] = 0;
    dfs2(1);
    vl f;
    for(i = 0; i < edges.size(); i++)
    {
        ll x = edges[i].f, y = edges[i].s;
        if(p[0][x] != y)
            swap(x, y);
        if(dist[x] >= 2 * k)
            f.pb(i+1);
    }
    cout << f.size() << "\n";
    for(auto u : f)
        cout << u << ' ';
    cout << "\n";
}
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    ll tests = 1;
    //cin >> tests;
    while(tests--)
    {
        solve();
    }
}

Compilation message (stderr)

railway.cpp: In function 'void solve()':
railway.cpp:122:18: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  122 |     for(i = 0; i < edges.size(); i++)
      |                ~~^~~~~~~~~~~~~~

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 7 / 7
• Subtask 4: 29 / 29
• Subtask 5: 16 / 16
• Subtask 6: 25 / 25