Submission #1275230

#	Time	Username	Problem	Language	Result	Execution time	Memory
1275230		vuquangsang	Railway (BOI17_railway)	C++20	100 / 100	116 ms	39748 KiB

railway

/*The best way to get something done is to begin*/
#include     <bits/stdc++.h>
#define     ll long long
#define     int long long
#define     fr(i,a,b) for(int i=a;i<=b;i++)
#define     frd(i,a,b) for(int i=a;i>=b;i--)
#define     pb push_back
#define     fi first
#define     se second
#define     el '\n'
using namespace std;
template <class X, class Y> bool minimize(X &x, const Y &y) {if (x > y) {x = y;return true;} else return false;}
template <class X, class Y> bool maximize(X &x, const Y &y) {if (x < y) {x = y;return true;} else return false;}
/* Author: Huynh Quoc Luat */
/*Khai Bao*/
const long long inf=1e18;
const int oo=1e9;
const int LO=21;
const int CH=27;
const int N=2e5+5;
const int sm=1e9+7;
int n,m,k;
vector <pair <int,int>> g[N];
//void add(int &x,const int &y){x+=y;if(x>=sm)x-=sm;}
//void sub(int &x,const int &y){x-=y;if(x<0)x+=sm;}

void read()
{
    cin >> n >> m >> k;
    fr(i,1,n-1){
        int x,y;
        cin >> x >> y;
        g[x].pb({y,i});
        g[y].pb({x,i});
    }
}

namespace sub1
{
    vector <int> adj[N];
    int in[N],out[N],P[N][LO];
    int h[N];
    int path[N];
    int cnt[N];
    int dem=0;
    bool cmp(int u,int v){
        return in[u] < in[v];
    }
    void dfs(int u,int p){
        in[u]=++dem;
        for(auto it:g[u]){
            int v=it.fi;
            int id=it.se;
            if(v==p) continue;
            h[v]=h[u]+1;
            P[v][0]=u;
            path[v]=id;
            dfs(v,u);
        }
        out[u]=dem;
    }
    int lca(int u,int v){
        if(h[u]<h[v]) swap(u,v);
        frd(i,__lg(n),0) if(h[P[u][i]]>=h[v]) u=P[u][i];
        frd(i,__lg(n),0) if(P[u][i]!=P[v][i]) u=P[u][i],v=P[v][i];
        if(u==v) return u;
        return P[u][0];
    }
    void update(int u,int p){
        for(auto v:adj[u]){
            if(v==p) continue;
            cnt[u]++;
            cnt[v]++;
            cnt[lca(u,v)]-=2;
            update(v,u);
        }
    }
    void DFS(int u,int p){
        for(auto it:g[u]){
            int v=it.fi;
            if(v==p) continue;
            DFS(v,u);
            cnt[u]+=cnt[v];
        }
    }
    vector <int> key;
    void process()
    {
        dfs(1,0);
        P[1][0]=1;
        fr(j,1,__lg(n)){
            fr(i,1,n) P[i][j]=P[P[i][j-1]][j-1];
        }
        while(m--){
            int x,y;
            cin >> x;
            key.clear();
            fr(i,1,x){
                cin >> y;
                key.pb(y);
            }
            sort(key.begin(),key.end(),cmp);
            int sz=key.size();
            fr(i,1,sz-1){
                key.pb(lca(key[i-1],key[i]));
            }
            sort(key.begin(),key.end(),cmp);
            key.resize(unique(key.begin(),key.end())-key.begin());
            deque <int> dq;
            for(auto v:key) adj[v].clear();
            for(auto v:key){
                while(!dq.empty() and out[dq.back()]<in[v]) dq.pop_back();
                if(dq.size()){
                    adj[dq.back()].pb(v);
                    adj[v].pb(dq.back());
                }
                dq.pb(v);
            }
            update(key[0],0);
        }
        DFS(1,0);
        vector <int> ans;
        fr(i,2,n) if(cnt[i]>=k){
            ans.pb(path[i]);
        }
        cout << ans.size() << el;
        sort(ans.begin(),ans.end());
        for(auto v:ans) cout << v << " ";
    }
}
void time()    {cerr<< endl<<"Luattapcode: "<<clock()<<"ms"<<endl;}
main()
{
    ios_base::sync_with_stdio(NULL);cin.tie(NULL);cout.tie(NULL);
    #define TASK "qn"
    if(fopen(TASK".INP","r"))
    {
        freopen(TASK".INP", "r", stdin);
        freopen(TASK".OUT", "w", stdout);
    }
    int mtt=0;
    int test=1;
    if(mtt) cin>>test;
    while(test--)
    {
        read();
        sub1::process();
    }
    time();
    return 0;
}

Compilation message (stderr)

railway.cpp:132:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
  132 | main()
      | ^~~~
railway.cpp: In function 'int main()':
railway.cpp:138:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  138 |         freopen(TASK".INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:139:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  139 |         freopen(TASK".OUT", "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