Submission #463933

#	Time	Username	Problem	Language	Result	Execution time	Memory
463933		bonopo	Railway (BOI17_railway)	C++14	100 / 100	111 ms	23824 KiB

railway

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
#define pb push_back
#define rc (i<<1)|1
#define lc (i<<1)
#define el "\n"
#define f first
#define s second

typedef long long ll;
const int MM=1e5+5, MOD=1e9+7, LOG=19;
int N, M, K, psa[MM], dep[MM], son[MM], top[MM], fa[MM], sz[MM], in[MM], ot[MM], cnt;
vector<pair<int,int>> adj[MM];
vector<int> vdj[MM], ans;

void df1(int u, int pa=0) {
    dep[u]=dep[pa]+1; fa[u]=pa; sz[u]=1; in[u]=++cnt;
    for(auto &e:adj[u]) if(e.f!=pa) {
        int v=e.f;
        df1(v, u); sz[u]+=sz[v];
        if(sz[v]>sz[son[u]]) son[u]=v; }
    ot[u]=++cnt;
}

void df2(int u, int pa=0) {
    if(son[u]) {
        top[son[u]]=top[u]; df2(son[u], u); }
    for(auto &e:adj[u]) if(e.f!=pa&&e.f!=son[u]) {
        df2(top[e.f]=e.f, u);
    }
}

bool above(int u, int v) {
    return in[u]<in[v]&&ot[v]<ot[u];
}

bool cmp(int u, int v) {
    return in[u]<in[v];
}

int lca(int u, int v) {
    for(; top[u]!=top[v]; u=fa[top[u]]) {
        if(dep[top[u]]<dep[top[v]]) swap(u, v); }
    return (dep[u]<dep[v]?u:v);
}

int buildvrt(vector<int> &vrt, int k) {
    sort(begin(vrt), end(vrt), cmp);
    for(int i=1; i<k; ++i) {
        vrt.pb(lca(vrt[i-1], vrt[i])); }
    sort(begin(vrt), end(vrt), cmp);
    vrt.erase(unique(begin(vrt), end(vrt)), end(vrt));
    vector<int> stk={vrt[0]};
    for(int i=1; i<vrt.size(); ++i) {
        int u=vrt[i];
        while(stk.size()>=2&&!above(stk.back(), u)) {
            vdj[stk[stk.size()-2]].pb(stk.back());
            stk.pop_back(); }
        stk.pb(u); }
    while(stk.size()>=2) {
        vdj[stk[stk.size()-2]].pb(stk.back());
        stk.pop_back(); }
    return stk[0];
}

void df3(int u, int pa=0) {
    for(int &v:vdj[u]) if(v!=pa) ++psa[v], --psa[u], df3(v, u);
    vdj[u].clear();
}

void df4(int u, int pa=0) {
    for(auto &e:adj[u]) if(e.f!=pa) {
        df4(e.f, u); psa[u]+=psa[e.f]; }
    for(auto &e:adj[u]) if(e.f!=pa) {
        if(psa[e.f]>=K) ans.pb(e.s);
    }
}

int32_t main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    cin>>N>>M>>K;
    for(int i=1, u, v; i<N; ++i) {
        cin>>u>>v;
        adj[u].pb({v,i}); adj[v].pb({u,i}); }
    df1(1); df2(top[1]=1);
    for(int i=1, k; i<=M; ++i) {
        cin>>k; vector<int> vrt;
        for(int j=1, x; j<=k; ++j) cin>>x, vrt.pb(x);
        df3(  buildvrt(vrt, k)); }
    df4(1);
    sort(begin(ans), end(ans));
    cout<<ans.size()<<el;
    for(int i=0; i<ans.size(); ++i) cout<<ans[i]<<" \n"[i==ans.size()-1];
}

// MM

Compilation message (stderr)

railway.cpp: In function 'int buildvrt(std::vector<int>&, int)':
railway.cpp:56:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   56 |     for(int i=1; i<vrt.size(); ++i) {
      |                  ~^~~~~~~~~~~
railway.cpp: In function 'int32_t main()':
railway.cpp:95:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   95 |     for(int i=0; i<ans.size(); ++i) cout<<ans[i]<<" \n"[i==ans.size()-1];
      |                  ~^~~~~~~~~~~
railway.cpp:95:58: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   95 |     for(int i=0; i<ans.size(); ++i) cout<<ans[i]<<" \n"[i==ans.size()-1];
      |                                                         ~^~~~~~~~~~~~~~

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