Submission #1082686

#TimeUsernameProblemLanguageResultExecution timeMemory
1082686WhisperFirefighting (NOI20_firefighting)C++17
31 / 100
214 ms35396 KiB
#include <bits/stdc++.h>

using namespace std;
using ll = long long;

#define int long long
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#define FORD(i, a, b) for (int i = (b); i >= (a); i --)
#define REP(i, a) for (int i = 0; i < (a); ++i)
#define REPD(i, a) for (int i = (a) - 1; i >= 0; --i)

#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)


constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

/*
    Phu Trong from Nguyen Tat Thanh High School for gifted student
*/

template <class X, class Y>
    bool minimize(X &x, const Y &y){
        X eps = 1e-9;
        if (x > y + eps) {x = y; return 1;}
        return 0;
    }

template <class X, class Y>
    bool maximize(X &x, const Y &y){
        X eps = 1e-9;
        if (x + eps < y) {x = y; return 1;}
        return 0;
    }
int N, K;
#define MAX                 300005

struct Edge{
    int u, v, w;
    Edge(){}
    Edge(int _u, int _v, int _w): u(_u), v(_v), w(_w){}

    int other(int x){
        return (x ^ u ^ v);
    }
} edge[MAX];
vector<int> G[MAX];
vector<int> ret;
pair<bool, int> dfs(int u, int p, int last_w){
    int mx = -INF, mn = 0;

    //mx khoảng đỉnh xa nhất có thể được bao phủ bởi 1 trạm nằm trong cây con gốc u
    //mn khoảng cách xa nhất của đỉnh chưa được bao phủ nằm trong cây con gốc u

    for (int&i : G[u]){
        int v = edge[i].other(u);
        if(v ^ p){
            pair<int, int> x = dfs(v, u, edge[i].w);
            if (x.first == 0) maximize(mn, x.second);
            else maximize(mx, x.second);
        }
    }
    if (mx >= mn){
        if(mx - last_w <= 0) return make_pair(0, 0);
        return make_pair(1, mx - last_w);
    }
    else{
        if (mn + last_w > K){
            ret.push_back(u);
            return make_pair(1, K - last_w);
        }
        else{
            return make_pair(0, mn + last_w);
        }
    }
}
void process(void){
    cin >> N >> K;
    for (int i = 1; i < N; ++i){
        cin >> edge[i].u >> edge[i].v >> edge[i].w;
        G[edge[i].u].emplace_back(i);
        G[edge[i].v].emplace_back(i);
    }
    dfs(1, 0, INF);
    cout << (int)ret.size() << '\n';
    for (int&i : ret) cout << i << " ";
}
signed main(){
    #define name "Whisper"
    cin.tie(nullptr) -> sync_with_stdio(false);
    //freopen(name".inp", "r", stdin);
    //freopen(name".out", "w", stdout);
    process();
    return (0 ^ 0);
}




#Verdict Execution timeMemoryGrader output
Fetching results...
#Verdict Execution timeMemoryGrader output
Fetching results...
#Verdict Execution timeMemoryGrader output
Fetching results...
#Verdict Execution timeMemoryGrader output
Fetching results...
#Verdict Execution timeMemoryGrader output
Fetching results...
#Verdict Execution timeMemoryGrader output
Fetching results...