Submission #935105

#	Time	Username	Problem	Language	Result	Execution time	Memory
935105		anton	Dreaming (IOI13_dreaming)	C++17	100 / 100	91 ms	37352 KiB

dreaming

#include<bits/stdc++.h>
#include "dreaming.h"

using namespace std;
#define pii pair<int, int>


struct Tree{
    vector<vector<pii>> adj;
    vector<pair<pii, pii>> longest;
    vector<int> furthest;
    int min_len = 1e9;
    int diameter= 0;
};
const int MAX_N= 1e5;
vector<pii> madj[MAX_N+2];
bool vis[MAX_N+2];
vector<Tree> forest;


Tree sTree;

void get_tree(int id, int anc){
    //cout<<id<<endl;
    vis[id] = true;
    int tree_id = sTree.adj.size();
    sTree.adj.push_back(vector<pii>(0));
    for(auto e: madj[id]){
        if(e.first!=anc){
            int future_id = sTree.adj.size();
            get_tree(e.first, id);
            sTree.adj[tree_id].push_back(pii(future_id, e.second));
            sTree.adj[future_id].push_back(pii(tree_id, e.second));
        }
    }
    //cout<<id<<" done "<<endl;
}

pii get_len(int id, int anc, Tree& tr){
    vector<pii> ch;
    ch.push_back({0, -1});
    ch.push_back({0, -1});

    int max_diam = 0;

    for(auto e: tr.adj[id]){
        if(e.first!=anc){
            pii ch_ans = get_len(e.first, id, tr);
            ch.push_back({ch_ans.first+e.second, e.first});
            max_diam = max(max_diam, ch_ans.second);
        }
    }

    sort(ch.begin(), ch.end());
    tr.longest[id] = {ch[ch.size()-1], ch[ch.size()-2]};
    return pii(ch[ch.size()-1].first, max(max_diam, ch[ch.size()-1].first+ch[ch.size()-2].first));
}

void dp_reroot(int id, int anc, int from_above, Tree& tr){
    //cout<<id<<endl;
    tr.furthest[id] = max(from_above, tr.longest[id].first.first);
    //cout<<id<<" "<<tr.furthest[id]<<endl;
    vector<pii> cands;
    cands.push_back(tr.longest[id].first);
    cands.push_back(tr.longest[id].second);
    cands.push_back({from_above, -1});
    sort(cands.begin(), cands.end());
    reverse(cands.begin(), cands.end());

    for(auto e: tr.adj[id]){
        if(e.first!=anc){
            if(e.first == cands[0].second){
                dp_reroot(e.first, id, cands[1].first + e.second, tr);
            }
            else{
                dp_reroot(e.first, id, cands[0].first + e.second, tr);
            }
        }
    }
}

pii find_center(Tree& tr){
    dp_reroot(0, -1, 0, tr);
    int res_id = 0;
    int res_dist = 1e9;
    for(int i = 0; i<tr.adj.size(); i++){
        if(tr.furthest[i]<res_dist){
            res_id =i;
            res_dist = tr.furthest[i];
        }
    }
    return {res_id, res_dist};
}



signed travelTime(signed N,signed M, signed L,signed A[], signed B[], signed T[]) {
    for(int i =0; i<M; i++){
        madj[A[i]].push_back(pii(B[i], T[i]));
        madj[B[i]].push_back(pii(A[i], T[i]));
    }

    fill(&vis[0], &vis[MAX_N], false);
    for(int i = 0; i<N; i++){
        /*for(auto e: madj[i]){
            cout<<e.first<<" ";
        }
        cout<<endl;*/
        if(!vis[i]){
            
            //cerr<<i<<endl;
            sTree.adj.clear();
            get_tree(i, -1);
            forest.push_back(sTree);
        }
    }

    //cout<<forest.size()<<endl;
    
    vector<int> radius;
    
    int res=  0;
    for(int j = 0; j<forest.size(); j++){
        forest[j].longest.resize(forest[j].adj.size());
        forest[j].furthest.resize(forest[j].adj.size());

        
        pii d =  get_len(0, -1, forest[j]);

        
        forest[j].diameter = d.second;
        res = max(res, forest[j].diameter);
        forest[j].min_len= find_center(forest[j]).second;
        radius.push_back(forest[j].min_len);
        //cout<<forest[j].diameter<<endl;
    }

    sort(radius.begin(), radius.end());

    if(radius.size()>1){
        res =max(res, radius[radius.size()-1]+radius[radius.size()-2]+L);
    }
    if(radius.size()>2){
        res =max(res, radius[radius.size()-2]+radius[radius.size()-3]+L*2);
    }
    return res;

}

Compilation message (stderr)

dreaming.cpp: In function 'std::pair<int, int> find_center(Tree&)':
dreaming.cpp:86:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<std::pair<int, int> > >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   86 |     for(int i = 0; i<tr.adj.size(); i++){
      |                    ~^~~~~~~~~~~~~~
dreaming.cpp: In function 'int travelTime(int, int, int, int*, int*, int*)':
dreaming.cpp:123:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<Tree>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  123 |     for(int j = 0; j<forest.size(); j++){
      |                    ~^~~~~~~~~~~~~~

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