Submission #449944

#	Time	Username	Problem	Language	Result	Execution time	Memory
449944		cpp219	Railway (BOI17_railway)	C++14	100 / 100	181 ms	29236 KiB

railway

#pragma GCC optimization O2
#pragma GCC optimization "unroll-loop"
#pragma target ("avx2")

#include <bits/stdc++.h>
#define ll int
#define ld long double
#define fs first
#define sc second
using namespace std;
typedef pair<ll,ll> LL;
const ll N = 1e5 + 9;
const ll Log2 = 21;
const ll inf = 1e9 + 7;

vector<ll> g[N];
ll n,Q,k,x,y,par[N][Log2],pos[N],child[N],nTime,d[N];
ll tot[N];

void DFS(ll u,ll p){
    child[u] = 1; pos[u] = nTime++;
    for (ll i = 1;i < Log2;i++) if ((1 << i) <= d[u])
        par[u][i] = par[par[u][i - 1]][i - 1];
    for (auto i : g[u]){
        if (i == p) continue;
        d[i] = d[u] + 1; par[i][0] = u;
        DFS(i,u); child[u] += child[i];
    }
}

ll LCA(ll u,ll v){
    if (d[u] > d[v]) swap(u,v);
    for (ll i = Log2 - 1;i >= 0;i--) if ((1 << i) <= d[v] && d[par[v][i]] >= d[u])
        v = par[v][i];
    if (u == v) return u;
    for (ll i = Log2 - 1;i >= 0;i--) if (par[u][i] != par[v][i])
        u = par[u][i],v = par[v][i];
    return par[u][0];
}

void reDFS(ll u,ll p){
    //cout<<u<<" "<<p<<"\n";
    for (auto i : g[u]) if (i != p){
        reDFS(i,u); tot[u] += tot[i];
    }
}

bool lf(ll x,ll y){
    return pos[x] < pos[y];
}
vector<LL> edge;

int main(){
    ios_base::sync_with_stdio(NULL); cin.tie(0); cout.tie(0);
    #define task "test"
    if (fopen(task".INP","r")){
        freopen(task".INP","r",stdin);
        //freopen(task".OUT","w",stdout);
    }
    cin>>n>>Q>>k;
    for (ll i = 1;i < n;i++){
        cin>>x>>y; edge.push_back({x,y});
        g[x].push_back(y); g[y].push_back(x);
    }
    DFS(1,0);
    while(Q--){
        vector<ll> v; ll sz,x;
        cin>>sz;
        for (ll i = 1;i <= sz;i++) cin>>x,v.push_back(x),tot[x]++;
        sort(v.begin(),v.end(),lf); tot[LCA(v[0],v.back())]--;
        for (ll i = 1;i < v.size();i++){
            ll cur = LCA(v[i],v[i - 1]); tot[cur]--;
        }
    }
    vector<ll> ans; reDFS(1,0);
    //for (ll i = 1;i <= n;i++) cout<<tot[i]<<" "; return 0;
    for (ll i = 0;i < n - 1;i++){
        ll x = edge[i].fs,y = edge[i].sc;
        if (pos[x] < pos[y]) swap(x,y);
        if (tot[x] >= k) ans.push_back(i + 1);
    }
    cout<<ans.size()<<"\n";
    for (auto i : ans) cout<<i<<" ";
}

Compilation message (stderr)

railway.cpp:1: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    1 | #pragma GCC optimization O2
      | 
railway.cpp:2: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    2 | #pragma GCC optimization "unroll-loop"
      | 
railway.cpp:3: warning: ignoring '#pragma target ' [-Wunknown-pragmas]
    3 | #pragma target ("avx2")
      | 
railway.cpp: In function 'int main()':
railway.cpp:71:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   71 |         for (ll i = 1;i < v.size();i++){
      |                       ~~^~~~~~~~~~
railway.cpp:57:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   57 |         freopen(task".INP","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

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