Submission #1110301

#	Time	Username	Problem	Language	Result	Execution time	Memory
1110301		guagua0407	Railway (BOI17_railway)	C++17	100 / 100	93 ms	26976 KiB

railway

//#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,int>
#define f first
#define s second
#define all(x) x.begin(),x.end()
#define _ ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

int dx[4]={0,0,1,-1};
int dy[4]={1,-1,0,0};

void setIO(string s) {
    freopen((s + ".in").c_str(), "r", stdin);
    freopen((s + ".out").c_str(), "w", stdout);
}

const int mxn=1e5+5;
vector<pair<int,int>> adj[mxn];
int st[mxn],en[mxn];
int cnt[mxn];
int depth[mxn];
int up[mxn][20];
int bit[mxn];
int res[mxn];
int timer=0;

void update(int pos,int val){
    for(;pos<mxn;pos+=(pos&-pos)){
        bit[pos]+=val;
    }
}

int query(int pos){
    int ans=0;
    for(;pos>0;pos-=(pos&-pos)){
        ans+=bit[pos];
    }
    return ans;
}

bool comp(int a,int b){
    return st[a]<st[b];
}

void dfs(int v,int p=0){
    st[v]=++timer;
    up[v][0]=p;
    depth[v]=depth[p]+1;
    for(auto u:adj[v]){
        if(u.f==p) continue;
        dfs(u.f,v);
    }
    en[v]=timer;
}

int lca(int a,int b){
    if(depth[a]<depth[b]) swap(a,b);
    int len=depth[a]-depth[b];
    for(int i=0;i<20;i++){
        if(len&(1<<i)) a=up[a][i];
    }
    if(a==b) return a;
    for(int i=19;i>=0;i--){
        int ta=up[a][i];
        int tb=up[b][i];
        if(ta!=tb){
            a=ta;
            b=tb;
        }
    }
    return up[a][0];
}

void dfs2(int v,int p=0){
    int prv=0;
    for(auto u:adj[v]){
        if(u.f==p) continue;
        dfs2(u.f,v);
        int val=query(en[v])-query(st[v]-1);
        res[u.s]=val-prv;
        prv=val;
    }
    update(st[v],cnt[v]);
}

int main() {_
    int n,m,k;
    cin>>n>>m>>k;
    for(int i=0;i<n-1;i++){
        int a,b;
        cin>>a>>b;
        adj[a].push_back({b,i});
        adj[b].push_back({a,i});
    }
    dfs(1);
    for(int j=1;j<20;j++){
        for(int i=1;i<=n;i++){
            up[i][j]=up[up[i][j-1]][j-1];
        }
    }
    for(int i=0;i<m;i++){
        int t;
        cin>>t;
        vector<int> vec(t);
        for(int j=0;j<t;j++){
            cin>>vec[j];
        }
        sort(all(vec),comp);
        for(int j=0;j<t;j++){
            int nxt=(j+1)%t;
            cnt[vec[j]]++;
            cnt[lca(vec[j],vec[nxt])]--;
        }
    }
    dfs2(1);
    vector<int> output;
    for(int i=0;i<n-1;i++){
        if(res[i]>=k){
            output.push_back(i+1);
        }
    }
    cout<<(int)output.size()<<'\n';
    for(auto v:output){
        cout<<v<<' ';
    }
    return 0;
}
//maybe its multiset not set
//yeeorz
//diaoborz

Compilation message (stderr)

railway.cpp: In function 'void setIO(std::string)':
railway.cpp:15:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 |     freopen((s + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:16:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |     freopen((s + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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