結果

問題 No.1833 Subway Planning
コンテスト
ユーザー woodywoody
提出日時 2022-09-21 02:57:09
言語 C++14
(gcc 13.3.0 + boost 1.87.0)
結果
WA  
実行時間 -
コード長 5,374 bytes
コンパイル時間 4,769 ms
コンパイル使用メモリ 241,648 KB
実行使用メモリ 70,676 KB
最終ジャッジ日時 2024-12-22 03:57:51
合計ジャッジ時間 39,675 ms
ジャッジサーバーID
（参考情報） 		judge2 / judge5
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 * 20 WA * 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 # 

// #define _GLIBCXX_DEBUG
#include<bits/stdc++.h>
#include<atcoder/all>
#define rep(i,b) for(int i=0;i<b;i++)
#define rrep(i,b) for(int i=b-1;i>=0;i--)
#define rep1(i,b) for(int i=1;i<b;i++)
#define repx(i,x,b) for(int i=x;i<b;i++)
#define rrepx(i,x,b) for(int i=b-1;i>=x;i--)
#define fore(i,a) for(auto i:a)
#define fore1(i,a) for(auto &i:a)
#define rng(x) (x).begin(), (x).end()
#define rrng(x) (x).rbegin(), (x).rend()
#define sz(x) ((int)(x).size())
#define pb push_back
#define fi first
#define se second
#define pcnt __builtin_popcountll

using namespace std;
using namespace atcoder;

using ll = long long;
using ld = long double;
template<typename T> using mpq = priority_queue<T, vector<T>, greater<T>>;
template<typename T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<typename T> bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<typename T> ll sumv(const vector<T>&a){ll res(0);for(auto&&x:a)res+=x;return res;}
bool yn(bool a) { if(a) {cout << "Yes" << endl; return 1;} else {cout << "No" << endl; return 0;}}
#define dame { cout << "No" << endl; return 0;}
#define dame1 { cout << -1 << endl; return 0;}
#define test(x) cout << "test" << x << endl;
#define deb(x,y) cout << x << " " << y << endl;
#define debp(p) cout << p.fi << " " << p.se << endl;
#define deb3(x,y,z) cout << x << " " << y << " " << z << endl;
#define deb4(x,y,z,x2) cout << x << " " << y << " " << z << " " << x2 << endl;
#define out cout << ans << endl;
#define outd cout << fixed << setprecision(20) << ans << endl;
#define outm cout << ans.val() << endl;
#define outv fore(yans , ans) cout << yans << "\n";
#define outdv fore(yans , ans) cout << yans.val() << "\n";
#define show(x) cerr<<#x<<" = "<<x<<endl;
#define showdeb(x,y) cerr<<#x<<" = "<<x<<" : "<<#y<<" = "<<y<<endl;
#define showv(v) {fore(vy , v) {cout << vy << " ";} cout << endl;}
#define showv2(v) fore(vy , v) cout << vy << "\n";
#define showvm(v) {fore(vy , v) {cout << vy.val() << " ";} cout << endl;}
#define showvm2(v) fore(vy , v) cout << vy.val() << "\n";
using pll = pair<ll,ll>;using pil = pair<int,ll>;using pli = pair<ll,int>;using pii = pair<int,int>;using pdd = pair<ld,ld>;
using tp = tuple<int ,int ,int>;
using vi = vector<int>;using vd = vector<ld>;using vl = vector<ll>;using vs = vector<string>;using vb = vector<bool>;
using vpii = vector<pii>;using vpli = vector<pli>;using vpll = vector<pll>;using vpil = vector<pil>;
using vvi = vector<vector<int>>;using vvl = vector<vector<ll>>;using vvs = vector<vector<string>>;using vvb = vector<vector<bool>>;
using vvpii = vector<vector<pii>>;using vvpli = vector<vector<pli>>;using vvpll = vector<vpll>;using vvpil = vector<vpil>;
using mint = modint998244353;
using vm = vector<mint>;
using vvm = vector<vector<mint>>;
vector<int> dx={1,0,-1,0,1,1,-1,-1},dy={0,1,0,-1,1,-1,1,-1};
ll gcd(ll a, ll b) { return a?gcd(b%a,a):b;}
ll lcm(ll a, ll b) { return a/gcd(a,b)*b;}
#define yes {cout <<"Yes"<<endl;}
#define yesr { cout <<"Yes"<<endl; return 0;}
#define no {cout <<"No"<<endl;}
#define nor { cout <<"No"<<endl; return 0;}
const double eps = 1e-10;
const ll LINF = 1001002003004005006ll;
const int INF = 1001001001;

struct edge{
    int from,to;
    ll cost;

    edge(int from_=0,int to_=0,ll cost_=0) : from(from_),to(to_),cost(cost_) {}
};

void solve(){
    int n; cin>>n;

    vector<vector<edge>> e(n);
    vector<edge> e2(n-1);
    unordered_map<ll,int> mp;
    rep(i,n-1){
        int a,b,c; cin>>a>>b>>c;
        a--; b--;
        e[a].pb(edge(a,b,c));
        e[b].pb(edge(b,a,c));
        e2[i] = edge(a,b,c);
        mp[(ll)a*n + b] = i;
        mp[(ll)b*n + a] = i;
    }

    auto check = [&](ll mid)->bool{
        bool ok = false;
        int root;

        rep(i,n-1){
            if (e2[i].cost > mid){
                ok = true;
                root = i;
                break;
            }
        }

        if (!ok) return true;

        int a = e2[root].from;
        int b = e2[root].to;

        vi flg(n-1);
        flg[root] = 2;

        // show(root);

        bool ok2;

        auto dfs = [&](auto dfs,int x,int pre)->void{

            ll p = (ll)x*n + pre;
            int pi = mp[p];

            flg[pi] = 1;
        
            fore(y , e[x]){
                if(y.to == pre) continue;

                if (y.cost > mid && ok){
                    ok2 = false;
                }
        
                dfs(dfs , y.to ,x);
            }

            if (e2[pi].cost > mid || ok){
                // show(x);
                ok = true;
                flg[pi] = 2;
            }else{
                flg[pi] = 0;
            }
        
            return;
        };

        ok = false;
        ok2 = true;
        dfs(dfs,a,b);
        ok = false;
        dfs(dfs,b,a);

        if (!ok2) return false;

        ll mn = LINF;
        ll mx = 0;

        rep(i,n-1){
            if (flg[i] == 2){
                // show(i);
                chmin(mn , e2[i].cost);
                chmax(mx , e2[i].cost);
            }else if(flg[i] == 1){
                assert(0);
            }
        }

        return (mx-mn) <= mid;
    };

    // yn(check(70));

    ll l=-1,u=INF;

    while(u-l > 1){
        ll mid = (l+u) / 2;

        if (check(mid)) u = mid;
        else l = mid;
    }

    cout << u << endl;
}

int main(){

    solve();

    return 0;
}
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