Submission #1115959

#	Time	Username	Problem	Language	Result	Execution time	Memory
1115959		KhoaDuy	Railway (BOI17_railway)	C++14	100 / 100	116 ms	58524 KiB

railway

#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define int long long
const int MAXN=1e5;
vector<vector<int>> graph(MAXN+1);
int paidx[MAXN+1];
int w[MAXN+1]={0};
int depth[MAXN+1];
vector<vector<int>> sparse(18);
int in[MAXN+1];
int out[MAXN+1];
vector<int> loga;
int cmp(int a,int b){
    if(depth[a]<depth[b]){
        return a;
    }
    return b;
}
void DFS(int u,int p){
    in[u]=sparse[0].size();
    loga.push_back(loga[loga.size()>>1]+1);
    sparse[0].push_back(u);
    for(int v:graph[u]){
        if(v!=p){
            depth[v]=depth[u]+1;
            DFS(v,u);
        }
    }
    out[u]=sparse[0].size()-1;
    if(p!=-1){
        loga.push_back(loga[loga.size()>>1]+1);
        sparse[0].push_back(p);
    }
}
int LCA(int u,int v){
    int l=in[u],r=in[v];
    if(l>r){
        swap(l,r);
    }
    return cmp(sparse[loga[r-l+1]][l],sparse[loga[r-l+1]][r-(1<<loga[r-l+1])+1]);
}
bool cmp2(int a,int b){
    return (in[a]<in[b]);
}
vector<int> ans;
int k;
void DFS2(int u,int p){
    for(int v:graph[u]){
        if(v!=p){
            DFS2(v,u);
            w[u]+=w[v];
        }
    }
    if(w[u]>=k){
        ans.push_back(paidx[u]);
    }
}
signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n,m;
    cin >> n >> m >> k;
    loga.push_back(-1);
    vector<pair<int,int>> edges;
    for(int i=0;i<n-1;i++){
        int a,b;
        cin >> a >> b;
        edges.push_back({a,b});
        graph[a].push_back(b);
        graph[b].push_back(a);
    }
    depth[1]=0;
    DFS(1,-1);
    for(int i=1;i<18;i++){
        for(int j=0;j+(1<<i)<=sparse[0].size();j++){
            sparse[i].push_back(cmp(sparse[i-1][j],sparse[i-1][j+(1<<(i-1))]));
        }
    }
    while(m--){
        int s;
        cin >> s;
        vector<int> a(s);
        for(int i=0;i<s;i++){
            cin >> a[i];
        }
        sort(a.begin(),a.end(),cmp2);
        for(int i=0;i+1<s;i++){
            a.push_back(LCA(a[i],a[i+1]));
        }
        sort(a.begin(),a.end(),cmp2);
        stack<int> st;
        for(int i=0;i<a.size();i++){
            if(i>0&&a[i]==a[i-1]){
                continue;
            }
            while(!st.empty()&&out[st.top()]<out[a[i]]){
                st.pop();
            }
            if(!st.empty()){
                int u=a[i],p=st.top();
                w[u]++;
                w[p]--;
            }
            st.push(a[i]);
        }
    }
    for(int i=0;i<edges.size();i++){
        int u=edges[i].first,v=edges[i].second;
        if(depth[u]>depth[v]){
            swap(u,v);
        }
        paidx[v]=i+1;
    }
    DFS2(1,-1);
    sort(ans.begin(),ans.end());
    cout << ans.size() << endl;
    for(int i=0;i<ans.size();i++){
        cout << ans[i] << ' ';
    }
}

Compilation message (stderr)

railway.cpp: In function 'int main()':
railway.cpp:76:29: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   76 |         for(int j=0;j+(1<<i)<=sparse[0].size();j++){
      |                     ~~~~~~~~^~~~~~~~~~~~~~~~~~
railway.cpp:93:22: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   93 |         for(int i=0;i<a.size();i++){
      |                     ~^~~~~~~~~
railway.cpp:108:18: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  108 |     for(int i=0;i<edges.size();i++){
      |                 ~^~~~~~~~~~~~~
railway.cpp:118:18: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  118 |     for(int i=0;i<ans.size();i++){
      |                 ~^~~~~~~~~~~

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