Submission #610924

#	Time	Username	Problem	Language	Result	Execution time	Memory
610924		beedle	Dreaming (IOI13_dreaming)	C++17	100 / 100	99 ms	22348 KiB

dreaming

#include "dreaming.h"
#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <set>
#include <iterator>
#include <stack>
#include <map>
#include <math.h>
#include <bitset>
#include <deque>
#include <string>
#include <tuple>
#include <queue>
#include <numeric>
#include <unordered_set>
#include <unordered_map>
#define pi 3.141592653589793238
#define ll long long
#define ld long double
#define rep(i, a, b) for (long long i = a; i <= b; i++)
#define mod 998244353ll
#define INF 1000000000000000000
#define pb push_back
#define ff first
#define ss second
#define endl '\n'
#define all(x) (x).begin (), (x).end ()
#define sz(x) (ll) (x).size ()
#define reunique(v) v.resize(std::unique(v.begin(), v.end()) - v.begin())
#define rank rnk
#define log lg
#define fast                                                                  \
    ios_base::sync_with_stdio (false);                                        \
    cin.tie (NULL);                                                           \
    cout.tie (NULL)
 
using namespace std;

ll maxdist;
ll maxvertex;

void dfs(int v, int p, vector <pair<ll,ll>> adj[], vector <bool> &marked, vector <ll> &d, vector <pair<ll,ll>> &par)
{
    marked[v]=true;

    if(p==-1)
    {
        d[v]=0;
        maxdist=0;
        maxvertex=v;
    }
    else
    {
        if(d[v]>maxdist)
        {
            maxdist=d[v];
            maxvertex=v;
        }
    }

    for(auto u:adj[v])
    if(u.ff!=p)
    {
        d[u.ff]=u.ss+d[v];
        par[u.ff]={v,u.ss};
        dfs(u.ff,v,adj,marked,d,par);
    }
}

int travelTime(int n, int m, int l, int a[], int b[], int t[]) {
    vector <pair<ll,ll>> adj[n+1];
    vector <bool> marked(n+1);
    vector <ll> d(n+1);
    vector <pair<ll,ll>> p(n+1);

    rep(i,0,m-1)
    {
        adj[a[i]].pb({b[i],t[i]});
        adj[b[i]].pb({a[i],t[i]});
    }

    vector <ll> w;

    ll g=0;

    rep(i,0,n-1)
    if(!marked[i])
    {
        dfs(i,-1,adj,marked,d,p);
        ll e1=maxvertex;
        dfs(e1,-1,adj,marked,d,p);
        ll e2=maxvertex;

        // cout<<e1<<" "<<e2<<" "<<maxdist<<endl;

        g=max(maxdist,g);

        if(e1==e2)
        {
            w.pb(0);
            continue;
        }

        ll v=e2;
        ll dnow=0;
        while(true)
        {
            ll last=dnow;
            dnow+=p[v].ss;
            v=p[v].ff;
            if(2*dnow>=maxdist)
            {
                w.pb(min(dnow,maxdist-last));
                break;
            }
        }
    }

    // for(auto x:w)
    // cout<<x<<" ";
    // cout<<endl;

    if(sz(w)==1)
    return g;
    else if(sz(w)==2)
    return max(g,w[0]+w[1]+l);
    else
    {
        sort(all(w));
        reverse(all(w));
        return max({w[0]+w[1]+l,w[1]+w[2]+2*l,g});
    }
}

// signed main()
// {
//     int n=12;
//     int m=8;
//     int l=2;
//     int a[]={0,8,2,5,5,1,1,10};
//     int b[]={8,2,7,11,1,3,9,6};
//     int t[]={4,2,4,3,7,1,5,3};
//     cout<<travelTime(n,m,l,a,b,t);
//     return 0;
// }

• Subtask 1: 14 / 14
• Subtask 2: 10 / 10
• Subtask 3: 23 / 23
• Subtask 4: 18 / 18
• Subtask 5: 12 / 12
• Subtask 6: 23 / 23