Submission #343537

#	Time	Username	Problem	Language	Result	Execution time	Memory
343537		katearima	Dreaming (IOI13_dreaming)	C++14	0 / 100	1099 ms	17132 KiB

dreaming

#include "dreaming.h"
#include <bits/stdc++.h>
#define ff first
#define ss second
using namespace std;
const int R=1e5+5;
vector<pair<int, int>> adj[R];
vector <bool> visited(R);
vector<int> trees[R], ans;
vector<pair<int, int>> par(R, {-1,0});
int t, distance;
typedef struct{
    int mx, start, dist;
} path;
typedef struct {
    int l , r,  val;
} ANS;
ANS answer;
void dfs (int k){
    trees[t].push_back(k);
    visited[k]=true;
    for(auto u:adj[k]){
        if(visited[u.ff]) continue;
        visited[u.ff]=true;
        dfs(u.ff);
    }

}
pair<int, int>  max_dist(int k, int par){
    vector <path> x(2);
    x[0].mx=0; x[1].mx=0;
    if(adj[k].size()<=1){
        x[1].start=k;
        x[0].start=k;
    }
    for(auto u:adj[k]){
        if(u.ff==par) continue;
        auto child=max_dist(u.ff,k);
        if(child.ff >= x[0].mx){
            x[1]=x[0];
            x[0]={child.ff, child.ss, u.ss};
        }
        else if(child.ff >= x[1].mx){
            x[1]={child.ff, child.ss, u.ss};
        }
    }

    if(x[0].mx+x[1].mx+x[0].dist+x[1].dist > answer.val){
        answer.val=x[0].mx+x[1].mx+x[0].dist+x[1].dist;
        answer.l=x[0].start;
        answer.r=x[1].start;
    }
    return {x[0].mx+x[0].dist, x[0].start};
}
void find_par(int k, int p){
    for(auto u:adj[k]){
        if(u.ff==p) continue;
        par[u.ff]=make_pair(k, u.ss);
        find_par(u.ff, k);
    }
}
int find_max(vector<int> v){
    answer.val=INT_MIN;
    max_dist(v[0], -1);
    int l=answer.l; int r=answer.r;
    par.clear(); par.resize(R);
    par[l]={-1,0};
    find_par(l, -1);
    /*for(int i=0; i<12; i++){
        cout<<i<<" "<<par[i].ff << " "<<par[i].ss<<endl;
    }*/
    vector<pair<int, int>> way;
    int k=answer.r;
    while(k!=-1){
        way.push_back({k, par[k].ss});
        k=par[k].ff;
    }
    reverse(way.begin(), way.end());
    int dist=answer.val;
    int max_distance=0;
    int x=0, y=INT_MAX; // x is distance   y is max apart?
    for(int i=0; i<way.size(); i++){
        int k=max(abs(dist/2 - x), abs(dist/2 - (dist-x)));
        if(k<y) {
            y=k;
            max_distance=max(x, dist-x);
        }
        x+=way[i].ss;
    }
    return max_distance;
    //cout<<max_distance<<endl;
    //cout<<"----"<<endl;
    //return answer.val;
}
int travelTime(int n, int m, int l, int a[], int b[], int time[]) {
    for(int i=0; i<m; i++){
        adj[a[i]].push_back(make_pair(b[i], time[i]));
        adj[b[i]].push_back(make_pair(a[i], time[i]));
    }
    t=0;
    for(int i=0; i<n; i++){
        if(visited[i]) continue;
        dfs(i);
        t++;
    }
    for(int i=0; i<t; i++){
        int k=find_max(trees[i]);
        //cout<<k<<endl;
        ans.push_back(k);
    }
    sort(ans.begin(), ans.end());
    reverse(ans.begin(), ans.end());
    if(t>2) return max(ans[1]+ans[2]+2*l, ans[0]+ans[1]+l);
    else if(t>1) return ans[0]+ans[1]+l;
    else return ans[0];
}

Compilation message (stderr)

dreaming.cpp: In function 'int find_max(std::vector<int>)':
dreaming.cpp:82:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   82 |     for(int i=0; i<way.size(); i++){
      |                  ~^~~~~~~~~~~
dreaming.cpp:65:25: warning: unused variable 'r' [-Wunused-variable]
   65 |     int l=answer.l; int r=answer.r;
      |                         ^

• Subtask 1: 0 / 14
• Subtask 2: 0 / 10
• Subtask 3: 0 / 23
• Subtask 4: 0 / 18
• Subtask 5: 0 / 12
• Subtask 6: 0 / 23