Submission #1210706

#	Time	Username	Problem	Language	Result	Execution time	Memory
1210706		vanea	Railway (BOI17_railway)	C++20	100 / 100	62 ms	22976 KiB

railway

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define LSOne(S) ((S) & (-S))

const int mxN = 1e5+10;

vector<array<int, 2>> adj[mxN];
int timer = 0, tin[mxN], tout[mxN], p_edge[mxN];
int anc[mxN][20], bit[mxN+50], d[mxN];

void dfs(int node, int p) {
    anc[node][0] = p;
    tin[node] = ++timer;
    for(int k = 1; k <= 18; k++) {
        anc[node][k] = anc[anc[node][k-1]][k-1];
    }
    for(auto [it, i] : adj[node]) {
        if(it == p) continue;
        p_edge[it] = i;
        d[it] = d[node]+1;
        dfs(it, node);
    }
    tout[node] = timer;
}

void jmp(int &x, int dist) {
    for(int k = 18; k >= 0; k--) {
        if(dist & (1 << k)) x = anc[x][k];
    }
}

int lca(int a, int b) {
    if(d[b] > d[a]) swap(a, b);
    jmp(a, d[a]-d[b]);
    if(a == b) return a;
    for(int k = 18; k >= 0; k--) {
        if(anc[a][k] != anc[b][k]) {
            a = anc[a][k];
            b = anc[b][k];
        }
    }
    return anc[a][0];
}

void upd(int x, int val) {
    for(; x <= mxN; x += LSOne(x)) {
        bit[x] += val;
    }
}

int qry(int x) {
    int ans = 0;
    for(; x >= 1; x -= LSOne(x)) {
        ans += bit[x];
    }
    return ans;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n, m, k;
    cin >> n >> m >> k;
    for(int i = 1; i < n; i++) {
        int a, b;
        cin >> a >> b;
        adj[a].push_back({b, i});
        adj[b].push_back({a, i});
    }
    dfs(1, 0);
    while(m--) {
        int s;
        cin >> s;
        vector<int> v(s+1);
        for(int i = 0; i < s; i++) {
            cin >> v[i];
        }
        sort(v.begin(), v.end()-1, [&](int a, int b) {
            return tin[a] < tin[b];
        });
        v[s] = v[0];
        for(int i = 0; i < s; i++) {
            int l = lca(v[i], v[i+1]);
            upd(tin[v[i]], 1);
            upd(tin[v[i+1]], 1);
            upd(tin[l], -2);
        }
    }
    vector<int> ans;
    for(int i = 1; i <= n; i++) {
        int now = qry(tout[i]) - qry(tin[i]-1);
        if(now >= 2*k) ans.push_back(p_edge[i]);
    }
    sort(ans.begin(), ans.end());
    cout << ans.size() << '\n';
    for(auto it : ans) {
        cout << it << ' ';
    }
    return 0;
}

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