Submission #966244

#	Time	Username	Problem	Language	Result	Execution time	Memory
966244		oblantis	Railway (BOI17_railway)	C++17	100 / 100	86 ms	27084 KiB

railway

//#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
//#pragma GCC optimize("O3,unroll-loops")
#include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define pb push_back
#define ss second
#define ff first
#define vt vector
#define uid(a, b) uniform_int_distribution<int>(a, b)(mt)
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int inf = 2e9;
const int mod = 1e9+7;
const int maxn = 1e5;
mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());
vt<int> g[maxn];
bool was[maxn];
int in[maxn], out[maxn], up[maxn][20], dp[maxn], cnt, p[maxn];
void dfs(int v){
    in[v] = cnt++;
    for(auto i : g[v]){
        if(i == up[v][0])continue;
        up[i][0] = v, dp[i] = dp[v] + 1;
        for(int j = 1; j < 20; j++)up[i][j] = up[up[i][j - 1]][j - 1];
        dfs(i);
    }
    out[v] = cnt++;
}
bool cmp(int x, int y){
    return in[x] < in[y];
}
void checkup(int v){
    for(auto i : g[v]){
        if(i == up[v][0])continue;
        checkup(i);
        p[v] += p[i];
    }
}
int lca(int x, int y){
    if(dp[x] > dp[y])swap(x, y);
    int k = dp[y] - dp[x], j = 0;
    while(k){
        if(k & 1){
            y = up[y][j];
        }
        k >>= 1, j++;
    }
    if(y == x)return x;
    for(int j = 19; j >= 0; j--){
        if(up[x][j] != up[y][j]){
            x = up[x][j], y = up[y][j];
        }
    }
    return up[x][0];
}
int nw, sz;
vt<int> c;
void go(int v){
    p[v]++;
    was[v] = 0;
    while(nw < sz && in[c[nw]] < out[v]){
        nw++;
        p[v]--;
        go(c[nw - 1]);
    }
}
void solve() {
    int n, m, k;
    cin >> n >> m >> k;
    int u[n - 1], v[n - 1];
    for(int i = 0; i < n - 1; i++){
        cin >> u[i] >> v[i];
        --u[i], --v[i];
        g[u[i]].pb(v[i]), g[v[i]].pb(u[i]);
    }
    dfs(0);
    for(int i = 0; i < m; i++){
        cin >> sz;
        c.resize(sz, 0);
        for(int j = 0; j < sz; j++){
            cin >> c[j];
            --c[j];
            was[c[j]] = 1;
        }
        sort(all(c), cmp);
        for(int j = 1; j < sz; j++){
            int LCA = lca(c[j], c[j - 1]);
            if(!was[LCA])c.pb(LCA), was[LCA] = 1;
        }
        sz = c.size();
        sort(all(c), cmp);
        nw = 1;
        go(c[0]);
        p[c[0]]--;
    }
    checkup(0);
    vt<int> ans;
    for(int i = 0; i < n - 1; i++){
        if(dp[u[i]] > dp[v[i]])swap(u[i], v[i]);
        if(p[v[i]] >= k){
            ans.pb(i + 1);
        }
    }
    cout << ans.size() << '\n';
    for(auto i : ans)cout << i << ' ';
}
int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    int times = 1; //cin >> times;
	for(int i = 1; i <= times; i++) {
		solve();
	}
	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