結果

問題 No.1833 Subway Planning
コンテスト
ユーザー shotoyoo
提出日時 2022-02-04 23:16:36
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
WA  
実行時間 -
コード長 7,316 bytes
コンパイル時間 3,112 ms
コンパイル使用メモリ 212,336 KB
最終ジャッジ日時 2025-01-27 19:51:55
ジャッジサーバーID
（参考情報） 		judge1 / judge1
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 * 19 WA * 1 TLE * 3
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 # 

 bool TEST = false;

using namespace std;
#include<bits/stdc++.h>
#include<fstream>

#define rep(i,n) for(ll (i)=0;(i)<(ll)(n);i++)
#define rrep(i,n) for(ll (i)=(ll)(n)-1;(i)>=0;i--)
#define range(i,start,end,step) for(ll (i)=start;(i)<(ll)(end);(i)+=(step))
#define rrange(i,start,end,step) for(ll (i)=start;(i)>(ll)(end);(i)+=(step))

#define dump(x)  cerr << "Line " << __LINE__ << ": " <<  #x << " = " << (x) << "\n";
#define spa << " " <<
#define fi first
#define se second
#define all(a)  (a).begin(),(a).end()
#define allr(a)  (a).rbegin(),(a).rend()

using ld = long double;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<ld, ld>;
 
template<typename T> using V = vector<T>;
template<typename T> using VV = V<V<T>>;
template<typename T, typename T2> using P = pair<T, T2>;
template<typename T, typename T2> using M = map<T, T2>;
template<typename T> using S = set<T>;
template<typename T, typename T2> using UM = unordered_map<T, T2>;
template<typename T> using PQ = priority_queue<T, V<T>, greater<T>>;
template<typename T> using rPQ = priority_queue<T, V<T>, less<T>>;
template<class T>vector<T> make_vec(size_t a){return vector<T>(a);}
template<class T, class... Ts>auto make_vec(size_t a, Ts... ts){return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));}
template<class SS, class T> ostream& operator << (ostream& os, const pair<SS, T> v){os << "(" << v.first << ", " << v.second << ")"; return os;}
template<typename T> ostream& operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<class T> ostream& operator<<(ostream& os, const vector<vector<T>> &v){ for(auto &e : v){os << e << "\n";} return os;}
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
 
template <class T> void UNIQUE(vector<T> &x) {sort(all(x));x.erase(unique(all(x)), x.end());}
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }
void fail() { cout << -1 << '\n'; exit(0); }
inline int popcount(const int x) { return __builtin_popcount(x); }
inline int popcount(const ll x) { return __builtin_popcountll(x); }
template<typename T> void debug(vector<vector<T>>&v){for(ll i=0;i<v.size();i++)
{cerr<<v[i][0];for(ll j=1;j<v[i].size();j++)cerr spa v[i][j];cerr<<"\n";}};
template<typename T> void debug(vector<T>&v){if(v.size()!=0)cerr<<v[0];
for(ll i=1;i<v.size();i++)cerr spa v[i];
cerr<<"\n";};
template<typename T> void debug(priority_queue<T>&v){V<T> vals; while(!v.empty()) {cerr << v.top() << " "; vals.push_back(v.top()); v.pop();} cerr<<"\n"; for(auto val: vals) v.push(val);}
template<typename T, typename T2> void debug(map<T,T2>&v){for(auto [k,v]: v) cerr << k spa v << "\n"; cerr<<"\n";}
template<typename T, typename T2> void debug(unordered_map<T,T2>&v){for(auto [k,v]: v) cerr << k spa v << "\n";cerr<<"\n";}
V<int> listrange(int n) {V<int> res(n); rep(i,n) res[i]=i; return res;}

template<typename T> P<T,T> divmod(T a, T b) {return make_pair(a/b, a%b);}

const ll INF = (1ll<<62);
// const ld EPS   = 1e-10;
// const ld PI    = acos(-1.0);


using VALUE = int;
VALUE unit = 1;

VALUE merge(VALUE val, VALUE other) {
  VALUE tmp;
  if (val==0 || other==0) tmp = 0;
  else if (val==2 && other==2) tmp = 0;
  else tmp = max(val, other);
  return tmp;
}
VALUE add_node(VALUE val, ll c, ll D, ll x) {
  VALUE tmp = val;
  if (c<D-x && c>x) {
      tmp = 0;
  } else if (c<D-x) {
      if (val==1) tmp = 1;
      else tmp = 0;
  } else if (c>x) {
      if (val==1) tmp = 2;
  }
  return tmp;
}

void Main(){
    // tree input (unweighted)
    int n,u,v;
    ll c;
    cin >> n;
    // unit = V<ll>();
    ll D = 0;
    VV<P<ll,int>> ns(n, V<P<ll,int>>());
    rep(i,n-1) {
        cin >> u >> v >> c;
        u--;
        v--;
        ns[u].emplace_back(c,v);
        ns[v].emplace_back(c,u);
        chmax(D, c);
    }
    int root = 0;
    rep(u,n) if (ns[u].size()>=2) {
        root = u;
        break;
    }
    auto sub = [&] (ll x) {
        V<VALUE> d0(n); // d0[u]: subtree u
        V<VALUE> d1(n); // d1[u]: subtree par[u]
        V<int> par(n, -1);
        V<int> pv(n, -1);
        par[root] = root;
        V<int> order;
        stack<int> s;
        s.push(root);
        while (!s.empty()) {
            auto u = s.top();
            s.pop();
            if (u<0) {
                u = ~u;
                auto val = unit;
                for (auto [c,v] : ns[u]) {
                if (par[v]!=u) continue;
                val = merge(val, add_node(d0[v], c, D, x));
                }
                d0[u] = val;
            } else {
                order.push_back(u);
                s.push(~u);
                for (auto [c,v]: ns[u]) {
                if (par[v]>=0) continue;
                if (c<D-x && c>x) return 0;
                s.push(v);
                par[v] = u;
                pv[v] = c;
                }
            }
        }
        d1[root] = unit;
        ll res = 0;
        for (auto u: order) {
            V<VALUE> cl = {unit};
            V<VALUE> cr = {unit};
            VALUE vl = unit;
            VALUE vr = unit;
            rep(i, ns[u].size()) {
                v = ns[u][i].second;
                auto c = ns[u][i].first;
                if (par[v]==u) {
                vl = merge(vl, add_node(d0[v], c, D, x));
                cl.push_back(vl);
                }
                v = ns[u][ns[u].size()-1-i].second;
                c = ns[u][ns[u].size()-1-i].first;
                if (par[v]==u) {
                vr = merge(vr, add_node(d0[v], c, D, x));
                cr.push_back(vr);
                }
            }
            reverse(all(cr));
            int i = 0;
            for (auto [c, v] : ns[u]) {
                if (par[v]!=u) continue;
                VALUE tmp = u==root? unit : add_node(d1[u], c, D, x);
                auto val = merge(merge(tmp, cl[i]), cr[i+1]);
                d1[v] = val;
                i++;
            }
        }
        // cout << x spa root << endl;
        // debug(d0);
        // debug(d1);
        int ok = 0;
        rep(u,n) {
            V<int> count(3);
            if (true) {
                auto c = pv[u];
                count[add_node(d1[u], c, D, x)]++;
            }
            for (auto [c,v] : ns[u]) {
                if (par[u]==v) {
                    count[add_node(d1[u], c, D, x)]++;
                } else { 
                    count[add_node(d0[v], c, D, x)]++;
                }
            }
            if (count[0]==0 && count[2]<=2) ok = 1;
            // cout << u << endl;
            // debug(count);
        }
        return ok;
    };
    ll ng = -1;
    ll ok = D;
    while (abs(ng-ok)>1) {
        ll mm = (ok+ng)/2;
        if (sub(mm)) ok = mm;
        else ng = mm;
    }
    cout << ok << endl;
}

int main(void){
    std::ifstream in("tmp_in");
    if (TEST) {
        std::cin.rdbuf(in.rdbuf());
        std::cout << std::fixed << std::setprecision(15);
    } else {
        std::cin.tie(nullptr);
        std::ios_base::sync_with_stdio(false);
        std::cout << std::fixed << std::setprecision(15);
    }
    Main();
}
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