Submission #523944

#	Time	Username	Problem	Language	Result	Execution time	Memory
523944		qwerasdfzxcl	Firefighting (NOI20_firefighting)	C++14	43 / 100	3073 ms	49048 KiB

Firefighting

#include <bits/stdc++.h>

typedef long long ll;
using namespace std;
vector<pair<int, ll>> adj[300300];
pair<int, ll> par[300300];
ll dep[300300];
int deg[300300], visited[300300];
priority_queue<pair<ll, int>> pq;

void dfs(int s, int pa = -1){
    deg[s] = adj[s].size();
    for (auto &v:adj[s]) if (v.first!=pa){
        par[v.first] = {s, v.second};
        dep[v.first] = dep[s] + v.second;
        dfs(v.first, s);
    }
}

int cnt;
void dfs2(int s, ll K){
    visited[s] = cnt;
    for (auto &v:adj[s]) if (visited[v.first]!=cnt){
        if (v.second<=K) dfs2(v.first, K-v.second);
        else{
            deg[v.first]--;
            if (deg[v.first]==1 && !visited[v.first]) pq.emplace(dep[v.first], v.first);
        }
    }
}

int main(){
    int n;
    ll D;
    scanf("%d %lld", &n, &D);
    for (int i=0;i<n-1;i++){
        int x, y;
        ll z;
        scanf("%d %d %lld", &x, &y, &z);
        adj[x].emplace_back(y, z);
        adj[y].emplace_back(x, z);
    }
    if (n==1) {printf("1\n1\n"); return 0;}

    dfs(1);
    for (int i=1;i<=n;i++) if (deg[i]==1) pq.emplace(dep[i], i);

    vector<int> ans;
    while(!pq.empty()){
        auto cur = pq.top(); pq.pop();
        if (visited[cur.second]) continue;

        int s = cur.second;
        ll rem = D;
        while(par[s].first && par[s].second<=rem){
            rem -= par[s].second;
            s = par[s].first;
        }
        ans.push_back(s);
        cnt++;
        dfs2(s, D);
    }

    printf("%d\n", (int)ans.size());
    for (auto &x:ans) printf("%d ", x);
    return 0;
}

Compilation message (stderr)

Firefighting.cpp: In function 'int main()':
Firefighting.cpp:35:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   35 |     scanf("%d %lld", &n, &D);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~
Firefighting.cpp:39:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   39 |         scanf("%d %d %lld", &x, &y, &z);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 3 / 3
• Subtask 2: 5 / 5
• Subtask 3: 9 / 9
• Subtask 4: 0 / 19
• Subtask 5: 26 / 26
• Subtask 6: 0 / 38