Submission #695257

#	Time	Username	Problem	Language	Result	Execution time	Memory
695257		Farhan_HY	Railway (BOI17_railway)	C++14	100 / 100	261 ms	147632 KiB

railway

#include <bits/stdc++.h>
#define int long long
#define float double
#define pb push_back
#define F first
#define S second
#define T int t; cin >> t; while(t--)
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    
using namespace std;
/// Benzema is the best player in the world
const int N = 1e6 + 6;
const int M = 3e4 + 3;
const int mod = 1e9 + 7;
const int inf = 1e18;
const int dx[] = {-1, 1, 0, 0};
const int dy[] = {0, 0, -1, 1};
const int LOG = 28;
int n, m, k, timer, par[N], in[N], depth[N], sp[N][LOG];
vector<pair<int, int>> adj[N];

void getDepth(int node, int pa) {
    par[node] = pa;
    in[node] = ++timer;
    depth[node] = depth[pa] + 1;
    for(auto x: adj[node])
        if (x.F != pa) getDepth(x.F, node);
}

void buildsparce() {
    for(int i = 1; i <= n; i++) sp[i][0] = par[i];
    for(int j = 1; j < 18; j++) {
        for(int i = 1; i <= n; i++)
            sp[i][j] = sp[sp[i][j - 1]][j - 1];
    }
}

int LCA(int u, int v) {
    if (depth[u] < depth[v]) swap(u, v);
    for(int i = 18; i >= 0; i--) {
        if (depth[u] == depth[v]) break;
        if (depth[sp[u][i]] >= depth[v])
            u = sp[u][i];
    }
    if (u == v) return u;
    for(int i = 18; i >= 0; i--) {
        if (sp[u][i] != sp[v][i])
            u = sp[u][i], v = sp[v][i];
    }
    return par[u];
}
set<int> st[N];
vector<int> ans, trees[N];

void dfs(int node, int par) {
    for(auto x: adj[node])   {
        if (x.F == par) continue;
        dfs(x.F, node);
        if (st[x.F].size() >= k)
            ans.push_back(x.S);
        if (st[node].size() < st[x.F].size())
            swap(st[x.F], st[node]);
        for(auto y: st[x.F])
            st[node].insert(y);
    }
    for(auto x: trees[node])
        st[node].erase(st[node].find(x));
}

main() {
    IOS
    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});
    }
    getDepth(1, 0);
    buildsparce();
    for(int i = 1; i <= m; i++) {
        int s;
        cin >> s;
        int p = 0;
        for(int j = 1; j <= s; j++) {
            int x;
            cin >> x;
            if (p != 0) p = LCA(p, x);
            else p = x;
            st[x].insert(i);
        }
        trees[p].push_back(i);
    }
    dfs(1, 0);
    cout << ans.size() << '\n';
    sort(begin(ans), end(ans));
    for(auto x: ans) cout << x << ' ';
}

Compilation message (stderr)

railway.cpp: In function 'void dfs(long long int, long long int)':
railway.cpp:59:28: warning: comparison of integer expressions of different signedness: 'std::set<long long int>::size_type' {aka 'long unsigned int'} and 'long long int' [-Wsign-compare]
   59 |         if (st[x.F].size() >= k)
      |             ~~~~~~~~~~~~~~~^~~~
railway.cpp: At global scope:
railway.cpp:70:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   70 | main() {
      | ^~~~

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