Submission #462613

#	Time	Username	Problem	Language	Result	Execution time	Memory
462613		JovanB	Railway (BOI17_railway)	C++17	100 / 100	155 ms	26928 KiB

railway

#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef long double ld;
 
const int MAXLOG = 18;
 
int par[100005][MAXLOG+1];
vector <pair <int, int>> graf[100005];
int depth[100005];
int in[100005];
int out[100005];
int x[100005];
int pre[100005];
 
vector <int> res;
 
int tajm;
 
void dfs_pre(int v, int parent){
    depth[v] = depth[parent] + 1;
    par[v][0] = parent;
    for(int j=1; j<MAXLOG; j++){
        par[v][j] = par[par[v][j-1]][j-1];
    }
    in[v] = ++tajm;
    for(auto d : graf[v]){
        int c = d.first;
        if(c != parent) dfs_pre(c, v);
    }
    out[v] = tajm;
}
 
bool is_parent(int a, int b){
    return in[a] <= in[b] && out[b] <= out[a];
}
 
bool cmp(int a, int b){
    return in[a] < in[b];
}
 
int k;
 
int lca(int a, int b){
    if(is_parent(a, b)) return a;
    if(is_parent(b, a)) return b;
    for(int j=MAXLOG-1; j>=0; j--){
        if(!is_parent(par[a][j], b)) a = par[a][j];
    }
    return par[a][0];
}
 
int dfs(int v){
    int tren = 0;
    int koji = 0;
    for(auto c : graf[v]){
        if(c.first != par[v][0]) tren += dfs(c.first);
        else koji = c.second;
    }
    tren += pre[v];
    if(tren >= k) res.push_back(koji);
    return tren;
}
 
int main(){
    ios_base::sync_with_stdio(false), cin.tie(0);
    cout.precision(10);
    cout << fixed;
 
    out[0] = 2e5;
    int n, m;
    cin >> n >> m >> k;
    for(int i=1; i<n; i++){
        int a, b;
        cin >> a >> b;
        graf[a].push_back({b, i});
        graf[b].push_back({a, i});
    }
    dfs_pre(1, 0);
    for(int i=1; i<=m; i++){
        int len;
        cin >> len;
        for(int j=1; j<=len; j++){
            cin >> x[j];
        }
        sort(x+1, x+1+len, cmp);
        int mn = n+5;
        int v = x[len];
        int kolko = 0;
        vector <int> sad;
        for(int j=len; j>=1; j--){
            v = lca(v, x[j]);
            if(out[x[j]] < mn){
                pre[x[j]]++;
                kolko++;
                mn = out[x[j]];
                sad.push_back(x[j]);
            }
        }
        for(int j=0; j<sad.size()-1; j++){
            pre[lca(sad[j], sad[j+1])]--;
        }
        pre[v]--;
    }
    dfs(1);
    sort(res.begin(), res.end());
    cout << res.size() << "\n";
    for(auto c : res) cout << c << " ";
    return 0;
}

Compilation message (stderr)

railway.cpp: In function 'int main()':
railway.cpp:101:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  101 |         for(int j=0; j<sad.size()-1; j++){
      |                      ~^~~~~~~~~~~~~

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