Submission #432116

#	Time	Username	Problem	Language	Result	Execution time	Memory
432116		SirCovidThe19th	Railway (BOI17_railway)	C++14	100 / 100	236 ms	22980 KiB

railway

#include <bits/stdc++.h>
using namespace std;

const int mx = 1e5+5, ml = 17;

int n, m, k, tin[mx], tout[mx], cnt = 0, up[ml][mx], depth[mx], weight[mx]; 
vector<pair<int, int>> adj[mx]; vector<int> ans;

void dfs(int node){
    tin[node] = ++cnt;
    for (int l = 1; l < ml; l++) up[l][node] = up[l-1][up[l-1][node]];
    for (pair<int, int> nxt : adj[node])
        if (nxt.first != up[0][node])
            depth[nxt.first] = depth[node]+1, up[0][nxt.first] = node, dfs(nxt.first);
    tout[node] = cnt;
}
bool isAnc(int a, int b){ 
    return tin[a] <= tin[b] and tout[a] >= tout[b]; 
}
int lca(int a, int b){
    if (isAnc(a, b)) return a; 
    if (isAnc(b, a)) return b;
    for (int l = ml-1; l >= 0; l--) 
        if (up[l][a] != 0 and !isAnc(up[l][a], b)) 
            a = up[l][a];
    return up[0][a];
}
int solve(int node){
    int ret = weight[node];
    for (pair<int, int> nxt : adj[node])
        if (nxt.first != up[0][node]){
            int val = solve(nxt.first); ret += val;
            if (val >= k) ans.push_back(nxt.second);
        }
    return ret;
}
int main(){
    cin >> n >> m >> k;
    for (int i = 1; i < n; i++){
        int a, b; cin >> a >> b;
        adj[a].push_back({b, i}); adj[b].push_back({a, i});
    }dfs(1);
    for (int i = 0; i < m; i++){
        int s; cin >> s; int cn[s+1];
        for (int j = 0; j < s; j++) cin >> cn[j];
        sort(cn, cn+s, [](int a, int b) { return tin[a] < tin[b]; } ); cn[s] = cn[0];
        for (int j = 0; j < s; j++) weight[lca(cn[j], cn[j+1])]--, weight[cn[j+1]]++;
    }solve(1); sort(ans.begin(), ans.end());
    cout<<ans.size()<<endl; for (int res : ans) cout<<res<<" ";
}

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