結果

問題 No.3113 The farthest point
コンテスト
ユーザー syndrome
提出日時 2025-04-19 22:03:34
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 501 ms / 2,000 ms
コード長 3,784 bytes
コンパイル時間 2,980 ms
コンパイル使用メモリ 237,004 KB
実行使用メモリ 74,212 KB
最終ジャッジ日時 2025-04-19 22:03:48
合計ジャッジ時間 11,562 ms
ジャッジサーバーID
（参考情報） 		judge5 / judge3
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 3
other AC * 33
権限があれば一括ダウンロードができます

ソースコード

diff # 

// (⁠◕⁠ᴗ⁠◕⁠✿⁠)

// #pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define srep(i, s, n) for (ll i = s; i < (n); i++)
#define len(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
using namespace std;
template<typename T> using vc = vector<T>;
template<typename T> using vv = vc<vc<T>>;
template<typename T> using vvv = vv<vc<T>>;
using vi = vc<int>;using vvi = vv<int>; using vvvi = vv<vi>;
using ll = long long;using vl = vc<ll>;using vvl = vv<ll>; using vvvl = vv<vl>;
using ld = long double; using vld = vc<ld>; using vvld = vc<vld>; using vvvld = vc<vvld>;
using uint = unsigned int;
using ull = unsigned long long;
const ld pi = acos(-1.0);
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
// const ll mod = 1000000007;
const ll mod = 998244353;
inline bool inside(ll y, ll x, ll H, ll W) {return 0 <= (y) and (y) < (H) and 0 <= (x) and (x) < (W); }

#define debug(var)  do{std::cout << #var << " : \n";view(var);}while(0)
template<typename T> void view(T e){cout << e << endl;}
template<typename T> void view(const vc<T>& v){for(const auto& e : v){ cout << e << " "; } cout << endl;}
template<typename T> void view(const vv<T>& vv){ for(const auto& v : vv){ view(v); } }
/*
merge -> merge children
f1 -> (already merged -> parent can merge)
f2 -> to ans
*/

using S = ll;
using T = ll;

T merge(T a, T b){return max(a, b);}
T f1(T a, int u, int v, S cost){return a + cost;}
T f2(T a, int v){return a;}
T e(){return 0;}
T leaf(int v){return 0;}

template <class S,
          class T,
          T (*merge)(T, T),
          T (*f1)(T, int, int, S),
          T (*f2)(T, int),
          T (*e)(),
          T (*leaf)(int)>
struct rerooting{
    public : 
        rerooting(vv<pair<int, S>> _g) : g(_g){
            N = len(g);
            acc1 = vc<T>(N, e());
            acc2 = vc<T>(N, e());
            res1 = vc<T>(N, e());
            res2 = vc<T>(N, e());
            acc_bef = vv<T>(N, {e()});
            acc_aft = vv<T>(N, {e()});
        }

        void dfs0(int v, int last = -1){
            vc<T> buildup;
            int cnt = 0;
            for (auto [u, c] : g[v]) if (u != last){
                cnt++;
                dfs0(u, v);
                res1[u] = f1(acc1[u], u, v, c);
                acc1[v] = merge(acc1[v], res1[u]);
                buildup.push_back(res1[u]);
            }
            if (cnt == 0) acc1[v] = leaf(v);
            for (int i = 0; i < len(buildup); i++) acc_bef[v].push_back(merge(acc_bef[v].back(), buildup[i]));
            for (int i = len(buildup) - 1; i >= 0; i--) acc_aft[v].push_back(merge(acc_aft[v].back(), buildup[i]));
        }

        void dfs1(int v, int last = -1){
            int w = 0;
            for (auto [u, c] : g[v]) if (u != last){
                acc2[u] = merge(merge(acc_bef[v][w], acc_aft[v][len(acc_aft[v]) - w - 2]), res2[v]);
                res2[u] = f1(acc2[u], v, u, c);
                dfs1(u, v);
                w++;
            }
        }

        vc<T> solve(){
            dfs0(0);
            dfs1(0);
            vc<T> ret(N);
            rep(v, N) ret[v] = f2(merge(acc1[v], res2[v]), v);
            return ret;
        }

    private : 
        int N;
        vv<pair<int, S>> g;
        vc<T> acc1, acc2, res1, res2;
        vv<T> acc_bef, acc_aft;
};

int main(){
    int N; cin >> N;
    vv<pair<int, ll>> g(N);
    rep(i, N - 1){
        int u, v; ll w; cin >> u >> v >> w;
        u--; v--;
        g[u].push_back({v, w});
        g[v].push_back({u, w});
    }
    rerooting<S, T, merge, f1, f2, e, leaf> dp(g);
    auto ret = dp.solve();
    ll ans = 0;
    for (auto x : ret) ans = max(ans, x);
    cout << ans << endl;
}
0