Submission #1125824

#	Time	Username	Problem	Language	Result	Execution time	Memory
1125824		wibulord	Railway (BOI17_railway)	C++20	36 / 100	88 ms	23744 KiB

railway

#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define pb emplace_back
#define ii pair<int, int>
#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
#define sz(s) (int)((s).size())
#define all(a) a.begin(), a.end()
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define F0R(i, b) for (int i = 0, _b = (b); i < _b; ++i)
#define FORd(i, a, b) for (int i = (a), _b = (b); i >= _b; --i)
#define F0Rd(i, b) for (int i = (b)-1; i >= 0; i--)
#define debug(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
using namespace std;

template<typename T1,typename T2> bool ckmax(T1 &x,const T2 &y){if(x<y){x=y; return 1;} return 0;}
template<typename T1,typename T2> bool ckmin(T1 &x,const T2 &y){if(y<x){x=y; return 1;} return 0;}

const int MOD = (int)1e9 + 7;
const int mod = 998244353;
const int N = 1e5 + 10, M = 19;
const long long INF = (long long)1e18 + 11;

/*
     /\_/\
    (= ._.)
    / >?  \>$
*/

int n, m, k, tms;
int idx[N], id[N], cnt[N];
int num[N], h[N], up[N][M];
vector<ii> adj[N];
vector<int> ans;

void dfs(int u, int p = -1){
    num[u] = ++tms;
    for(auto [v, e] : adj[u]) if(v != p){
        id[v] = e;
        h[v] = h[u] + 1, up[v][0] = u;
        FOR(i, 1, __lg(h[v])) up[v][i] = up[up[v][i-1]][i-1];
        dfs(v, u);
    }
}

int lca(int u, int v){
    if(h[u] != h[v]){
        if(h[u] < h[v]) swap(u, v);
        int k = h[u] - h[v];
        F0Rd(i, __lg(k)+1) if((k >> i) & 1) u = up[u][i];
    }
    if(u == v) return u;
    F0Rd(i, __lg(h[u])+1) if(up[u][i] != up[v][i]) u = up[u][i], v = up[v][i];
    return up[u][0];
}

void DFS(int u, int p = -1){
    for(auto [v, e] : adj[u]) if(v != p){
        DFS(v, u);
        cnt[u] += cnt[v];
    }
}

void sol(void){
    cin >> n >> m >> k;
    FOR(i, 1, n-1){
        int u, v; cin >> u >> v;
        adj[u].pb(v,i), adj[v].pb(u,i);
    }
    dfs(1);
    FOR(i, 1, m){
        int s; cin >> s;
        FOR(i, 1, s) cin >> idx[i];
        sort(idx+1, idx+s+1, [&](const int &x, const int &y){
            return num[x] < num[y];
        });
        FOR(i, 1, s-1){
            cnt[idx[i]]++, cnt[idx[i+1]]++;
            cnt[lca(idx[i], idx[i+1])] -= 2;
//            cout << idx[i] << ' ' << idx[i+1] << ' ' << lca(idx[i], idx[i+1]) << '\n';
        }
//        FOR(i, 1, s) cout << idx[i] << " \n"[i == s];
//        return;
    }
    DFS(1);
    FOR(i, 1, n) if(cnt[i] >= k) ans.push_back(id[i]);
    cout << sz(ans) << '\n';
    for(int i : ans) cout << i << ' ';
}

signed main(void){
    #define TASK "nhap"
    if(fopen(TASK".inp", "r")){
        freopen(TASK".inp", "r", stdin);
        freopen(TASK".out", "w", stdout);
    }
    ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
    int t = 1;
//    cin >> t;
    while(t--) sol();
    cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << " ms\n";
}

Compilation message (stderr)

railway.cpp: In function 'int main()':
railway.cpp:96:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   96 |         freopen(TASK".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:97:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   97 |         freopen(TASK".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 8
• Subtask 2: 0 / 15
• Subtask 3: 7 / 7
• Subtask 4: 29 / 29
• Subtask 5: 0 / 16
• Subtask 6: 0 / 25