Submission #943948

#	Time	Username	Problem	Language	Result	Execution time	Memory
943948		vjudge1	Railway (BOI17_railway)	C++17	100 / 100	153 ms	47984 KiB

railway

#include <bits/stdc++.h>
using namespace std;
// typedefs...
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll, ll> pll;
// constants...
const double PI = acos(-1);
const ll mod = 1000000007; // 998244353
const ll INF = 1e9+5;
const ll INFLL = 1e18+5;
// defines...
#define PB        push_back
#define fi         first
#define se         second
#define boost_      ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0);
#define endl '\n'

// functions...
ll gcd(ll a, ll b){ while (b){ a %= b; swap(a, b);} return a;}
ll lcm(ll a, ll b){ return (a/gcd(a, b)*b);}
ll modpow(ll a,ll p,ll mod) {ll ans=1;while(p){if(p%2)ans=(ans*a)%mod;a=(a*a)%mod;p/=2;} return ans;}
ll inverse_mod(ll n,ll mod) {return modpow(n,mod-2,mod);}

const int N= 1e5+5,LOG= 18;
int depth[N],up[N][LOG], sz[N];
vector<pii> v[N];
vector<int> col[N], minister[N];
void dfs(int pos,int pre) {
   sz[pos] = 1;
   for(auto it:v[pos]) {
      if(it.fi==pre) continue;
      depth[it.fi]=depth[pos]+1;
      up[it.fi][0] = pos; 
      for(int j = 1; j < LOG; j++) 
      {
        up[it.fi][j] = up[up[it.fi][j-1]][j-1];
      }
      dfs(it.fi,pos);
      sz[pos] += sz[it.fi];
   }
   return ;
}
int kthancestor(int pos,int k) {
    for(int i=LOG-1;i>=0;i--) {
        if(k&(1<<i))
        pos=up[pos][i];
    }
    return pos;
}
int get_lca(int a, int b)  { 
    if(depth[a] < depth[b]) {
        swap(a, b);
    }
    // 1) Get same depth.
    int k = depth[a] - depth[b];
    a=kthancestor(a,k);
    // 2) if b was ancestor of a then now a==b
    if(a == b) {
        return a;
    }
    // 3) move both a and b with powers of two
    for(int j = LOG - 1; j >= 0; j--) {
        if(up[a][j] != up[b][j]) {
            a = up[a][j];
            b = up[b][j];
        }
    }
    return up[a][0];
}
int n, m, k;
set<int> subtree[N], ans;
void dfs_seg(int pos, int pre, int ind) {
    
    for(auto it : v[pos]) {
        if(it.fi == pre) continue;
        dfs_seg(it.fi, pos, it.se);
        if(subtree[pos].size() < subtree[it.fi].size())
        swap(subtree[pos], subtree[it.fi]);
        for(auto itt : subtree[it.fi]) {
            subtree[pos].insert(itt);
        }
    }
    for(auto it : col[pos]) subtree[pos].insert(it);
    for(auto it : minister[pos]) subtree[pos].erase(it);
    if(subtree[pos].size() >= k) ans.insert(ind);
}

void solve() {

    
    cin >> n >> m >> k;
    for(int i = 1; i < n; i++) {
        int x, y;
        cin >> x >> y;
        v[x].PB({y, i}); v[y].PB({x, i});
    }
    dfs(1, 1);
    for(int i = 1; i <= m; i++) {
        int x, y, lc;
        cin >> x;
        vector<int> temp(x);
        for(int j = 0; j < x; j++) cin >> temp[j];
        for(int j = 0; j < x; j++) {
            if(j == 0) lc = temp[j];
            else lc = get_lca(lc, temp[j]);
            // cout << i << lc << endl;
        }
        minister[lc].PB(i);
        for(int j = 0; j < x; j++) {
            col[temp[j]].PB(i);
        }
    }
    dfs_seg(1, 1, 0);
    ans.erase(0);
    cout << ans.size() << endl;
    for(auto it : ans) cout << it << " ";
    cout << endl;
}
int main()
{
    boost_;
    int t = 1;
    // cin >> t;
    for(int i=1;i<=t;i++)
    {
        // cout<<"Case "<<i<<":\n";
        solve();
    }
}

Compilation message (stderr)

railway.cpp: In function 'void dfs_seg(int, int, int)':
railway.cpp:87:28: warning: comparison of integer expressions of different signedness: 'std::set<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   87 |     if(subtree[pos].size() >= k) ans.insert(ind);
      |        ~~~~~~~~~~~~~~~~~~~~^~~~
railway.cpp: In function 'void solve()':
railway.cpp:101:16: warning: unused variable 'y' [-Wunused-variable]
  101 |         int x, y, lc;
      |                ^

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