Submission #524179

#	Time	Username	Problem	Language	Result	Execution time	Memory
524179		Cross_Ratio	Firefighting (NOI20_firefighting)	C++14	0 / 100	268 ms	28096 KiB

Firefighting

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int INF = 1e18;
typedef pair<int,int> P;
vector<vector<P>> adj;
bool type[300005];
vector<int> ans;
int K;
int dfs(int c, int p, int len) {
    int m1 = 0, m2 = 0, mi = INF;
    for(P n2 : adj[c]) {
        int n = n2.first;
        int d = n2.second;
        if(n==p) continue;
        int len = dfs(n, c, d);
        if(type[n]) mi = min(mi, len); // sobang case
        else {
            if(len >= m1) {
                m2 = m1;
                m1 = len;
            }
            else if(len > m2) m2 = len;
        }
    }
    if(mi == INF) {
        if(len == -1 || m1 + len > K || m1 + m2 > K) {
            type[c] = true;
            ans.push_back(c);
            return len;
        }
        type[c] = false;
        return len + m1;
    }
    if(mi + m1 > K) {
        type[c] = true;
        ans.push_back(c);
        return len;
    }
    if(mi + len <= K) {
        type[c] = true;
        return mi + len;
    }
    type[c] = false;
    return len;
}
signed main() {
    cin.sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int N;
    cin >> N >> K;
    int i;
    adj.resize(N);
    if(N==1) {
        cout << 0;
        return 0;
    }
    for(i=0;i<N-1;i++) {
        int a, b, c;
        cin >> a >> b >>c;
        adj[a-1].push_back(P(b-1, c));
        adj[b-1].push_back(P(a-1, c));
    }
    dfs(0, -1, -1);
    cout << ans.size() << '\n';
    for(i=0;i<ans.size();i++) cout << ans[i] + 1 << ' ';
}

Compilation message (stderr)

Firefighting.cpp: In function 'int main()':
Firefighting.cpp:67:14: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   67 |     for(i=0;i<ans.size();i++) cout << ans[i] + 1 << ' ';
      |             ~^~~~~~~~~~~

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