Submission #987818

#	Time	Username	Problem	Language	Result	Execution time	Memory
987818		Acanikolic	Railway (BOI17_railway)	C++14	100 / 100	231 ms	37300 KiB

railway

#include <bits/stdc++.h>

#define pb push_back

#define S second

#define F first

const int N = 1e5 + 10;

const int inf = 2e9;

const int lg = 17;

using namespace std;

vector<int>g[N];
int in[N],out[N],timer = 0,up[N][lg],n,f[N];

void dfs(int x,int par) {
    in[x] = ++timer;
    up[x][0] = par;
    for(int j = 1; j < lg; j++) up[x][j] = up[up[x][j - 1]][j - 1];
    for(auto X : g[x]) {
        if(X == par) continue;
        dfs(X,x);
    }
    out[x] = timer;
}

void DFS(int x,int par) {
    for(auto X : g[x]) {
        if(X == par) continue;
        DFS(X,x);
        f[x] += f[X];
    }
}

bool intree(int u,int v) {
    return (in[u] <= in[v] && out[u] >= out[v]);
}

int lca(int u,int v) {
    if(intree(u,v)) return u;
    if(intree(v,u)) return v;
    for(int j = lg - 1; j >= 0; j--) {
        if(up[u][j] > 0 && !intree(up[u][j],v)) u = up[u][j];
    }
    return up[u][0];
}

bool cmp(int A,int B) {
    return (in[A] <= in[B]);
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int m,k;
    cin >> n >> m >> k;
    map<pair<int,int>,int>index;
    for(int i = 1; i < n; i++) {
        int u,v;
        cin >> u >> v;
        index[{u,v}] = i;
        index[{v,u}] = i;
        g[u].pb(v);
        g[v].pb(u);
    }
    dfs(1,0);
    for(int q = 1; q <= m; q++) {
        int s;
        cin >> s;
        vector<int>b;
        for(int i = 0; i < s; i++) {
            int x;
            cin >> x;
            b.pb(x);
        }
        sort(b.begin(),b.end(),cmp);
        b.pb(b[0]);
        for(int i = 0; i < s; i++) {
            f[b[i]] += 1;
            f[b[i + 1]] += 1;
            f[lca(b[i],b[i + 1])] -= 2;
        }
    }
    DFS(1,0);
    vector<int>ans;
    for(int i = 1; i <= n; i++) {
        if(f[i] >= k * 2) {
            ans.push_back(index[{i,up[i][0]}]);
        }
    }
    sort(ans.begin(),ans.end());
    cout << ans.size() << "\n";
    for(auto X : ans) cout << X << " ";
    return 0;
}

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