Submission #1097056

#	Time	Username	Problem	Language	Result	Execution time	Memory
1097056		YasuaFullAp	Railway (BOI17_railway)	C++14	100 / 100	107 ms	27592 KiB

railway

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

#define ll long long
#define pi pair<int,int>
#define pii pair<int,pair<int,int>>
#define fi first
#define se second

const int N = 1e5 + 5;
const int LG = 20;
int p[N][LG + 2], tin[N], tout[N], timer, n, m, k, inc[N], de[N], dep[N], val[N], a[N];
vector<pi> adj[N];

void dfs1(int u, int par){
    for(int k = 1; k < LG; k++)
        p[u][k] = p[p[u][k - 1]][k - 1];

    tin[u] = ++timer;
    for(auto x:adj[u]){
        if(x.fi == par) continue;
        int v = x.fi;
        p[v][0] = u;
        dep[v] = dep[u] + 1;
        dfs1(v, u);
    }
    tout[u] = timer;
}

bool ances(int u, int v){
    return tin[u] <= tin[v] && tout[u] > tout[v];
}

int lca(int u, int v){
    if(u == v) return u;
    if(dep[u] < dep[v]) swap(u, v);

    for(int k = LG - 1; k >= 0; k--)
        if(dep[p[u][k]] >= dep[v]) u = p[u][k];
    if(u == v) return u;

    for(int k = LG - 1; k >= 0; k--)
        if(p[u][k] != p[v][k]) u = p[u][k], v = p[v][k];
    return p[u][0];
}

void dfs2(int u, int par){
    for(auto x:adj[u]){
        int id = x.se;
        int v = x.fi;
        if(v == par) continue;
        dfs2(v, u);
        inc[u] += inc[v];
        val[id] = inc[v];
      //  cout << u << ' ' << v << ' ' << inc[v] << '\n';
    }
    inc[u] -= de[u];
}

void UP(int u, int v){
    inc[v]++;
    de[u]++;
}

bool cmd(int u, int v){
    return tin[u] < tin[v];
}
signed main(){
   cin.tie(0)->sync_with_stdio(false);
  // freopen("IN.INP","r",stdin);
   // freopen("OU.OUT","w",stdout);
    cin >> n >> m >> k;
    for(int i = 1; i < n; i++){
        int u, v; cin >> u >> v;
        adj[u].push_back({v, i});
        adj[v].push_back({u, i});
    }      

    dep[1] = 1;
    dfs1(1, 0);
  //  cout << lca(2, 5) << '\n';
    for(int k = 1; k <= m; k++){
        int x; cin >> x;
        for(int i = 1; i <= x; i++) cin >> a[i];
        sort(a + 1, a + x + 1, cmd);
        int _lca = a[1];
        for(int i = 2; i <= x; i++){
          //  cout << a[i] << ' ';
            if(ances(a[i - 1], a[i])){
                UP(a[i - 1], a[i]);
            }else{
                int tmp = lca(_lca, a[i]);
                if(tmp == _lca){
                    UP(lca(a[i - 1], a[i]), a[i]);
                }else{
                    UP(tmp, _lca);
                    UP(tmp, a[i]);
                    _lca = tmp;
                }
            }
        }
       // cout << '\n';
      //  for(int i = 1; i <= n; i++) cout <<i << ' '<< inc[i] << ' ' << de[i] << '\n';

    }


    dfs2(1, 0);
    std::vector<int> vec;
    for(int i = 1; i < n; i++)
        if(val[i] >= k) vec.push_back(i);
    cout << vec.size() << '\n';
    for(auto x:vec) cout << x << ' ';
}

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