Submission #959539

#	Time	Username	Problem	Language	Result	Execution time	Memory
959539		Blagoj	Firefighting (NOI20_firefighting)	C++17	100 / 100	246 ms	44172 KiB

Firefighting

#include <bits/stdc++.h>

using namespace std;

#define endl '\n'
#define ll long long
#define all(x) (x).begin(), (x).end()

const int mxn = 3e5 + 10;

ll n, k;

vector<pair<ll, ll>> g[mxn];
vector<int> ans;

pair<bool, ll> dfs(int cur, int par = -1, ll dist = 1e16) {
    ll mxOver = -1e16, mxUnder = 0;
    for (auto [to, weight] : g[cur]) {
        if (to == par) continue;
        auto res = dfs(to, cur, weight);
        if (res.first) mxOver = max(mxOver, res.second);
        else mxUnder = max(mxUnder, res.second);
    }
    pair<bool, ll> res;
    if (mxOver >= mxUnder) res = {1, mxOver - dist};
    else res = {0, mxUnder + dist};
    if (!res.first && res.second > k) {
        res = {1, k - dist};
        ans.push_back(cur);
    }
    if (res.first && res.second < 0) res = {0, 0};
    return res;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin >> n >> k;
    for (int i = 0; i < n - 1; i++) {
        ll f, t, w;
        cin >> f >> t >> w;
        g[f].push_back({t, w});
        g[t].push_back({f, w});
    }
    dfs(1);
    cout << ans.size() << endl;
    for (auto x : ans) cout << x << " ";
}

• Subtask 1: 3 / 3
• Subtask 2: 5 / 5
• Subtask 3: 9 / 9
• Subtask 4: 19 / 19
• Subtask 5: 26 / 26
• Subtask 6: 38 / 38