Submission #339109

#	Time	Username	Problem	Language	Result	Execution time	Memory
339109		bigDuck	Race (IOI11_race)	C++14	0 / 100	4 ms	5100 KiB

race

#include "race.h"
#include<bits/stdc++.h>
using namespace std;
#define INIT  ios_base :: sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define mp make_pair
#define pb push_back
#define ft first
#define sc second
#define ll long long
#define pii pair<int, int>
#define count_bits __builtin_popcount

int n, k;
vector<pii> g[200010];
bool v[200010];
int res=1e9;







int subtask_2(int s, int l, int h){
int res=1e9;
    if(l>k){
            v[s]=false;
        return res;
    }
    if(l==k){
            v[s]=false;
        return h;
    }
    v[s]=true;
    for(pii pr:g[s]){
        int u=pr.ft, d=pr.sc;
        if(!v[u]){
            res=min(subtask_2(u, l+d, h+1), res);
        }
    }
    v[s]=false;
    return res;
}










map<pii, int> h;
int sz[200010];

void build_sz(int s){
    v[s]=true;
    sz[s]=1;
    for(pii u:g[s]){
        if(!v[u.ft]){
            build_sz(u.ft);
            sz[s]+=sz[u.ft];
        }
    }
    v[s]=false;
    return;
}



pii find_centroids(int s, int total){
    v[s]=true;

    if( abs(total-sz[s]*2)<=1 ){
         int mx=0, u;
        for(pii node:g[s]){

            if( (sz[node.ft]>mx) && (!v[node.ft]) ){
                mx=sz[node.ft];
                u=node.ft;
            }
            if(  (v[node.ft]) && ( (total-sz[node.ft]+1)>mx ) ) {
                mx=(total-sz[node.ft]+1);
                u=node.ft;
            }
        }
        return {u, s};
    }




            int mx=0, u;
        for(pii node:g[s]){

            if( (sz[node.ft]>mx) && (!v[node.ft]) ){
                mx=sz[node.ft];
                u=node.ft;
            }
        }
    pii res;
     res=find_centroids(u, total);

    v[s]=false;
    return res;
}


int path(int s, int l, int h){
int res=1e9;
    if(l>k){
        v[s]=false;
        return res;
    }
    if(l==k){
            v[s]=false;
        return h;
    }
    v[s]=true;
    for(pii pr:g[s]){
        int u=pr.ft, d=pr.sc;
        if(!v[u]){
            res=min(path(u, l+d, h+1), res);
        }
    }
    v[s]=false;
    return res;
}



void remove_edge(pii e){
int u=e.ft, v=e.sc;
int d=h[{u, v}];
g[u].erase(find(g[u].begin(), g[u].end(),mp(v, d) ));
g[v].erase(find(g[v].begin(), g[v].end(),mp(u, d) ));
}



void subtask_4(){
queue<int> forest;
forest.push(1);

while(!forest.empty()){
    int node=forest.front(); forest.pop();
    build_sz(node);
    //cout<<node<<"\n"<<flush;
    if(sz[node]==1){continue;}
    pii e=find_centroids(node, sz[node]);
    //cout<<e.ft<<" "<<e.sc<<"\n"<<flush;
    res=min(path(e.ft, 0, 1), res); res=min(path(e.sc, 0, 1), res);
    remove_edge(e);
    forest.push(e.ft); forest.push(e.sc);
}


}








int best_path(int N, int K, int H[][2], int L[])
{
  n=N; k=K;

  for(int i=0; i<(n-1); i++){
    int u=H[i][0]+1, v=H[i][1]+1, d=L[i];
    g[u].pb({v, d}); g[v].pb({u, d});
    h[{u, v} ]=d; h[{v, u} ]=d;
  }


    /*if( (k<=100) ){    subtask_3(1);}
    else{
        if(n<=1000){
        for(int i=1; i<=n; i++){
            res=min(res, subtask_2(i, 0, 1));
        }
        }
        else{
            subtask_4();
        }
    }*/
    subtask_4();

  if(res==(1e9)){
    return -1;
  }
  return res-1;
}

Compilation message (stderr)

race.cpp: In function 'std::pair<int, int> find_centroids(int, int)':
race.cpp:103:33: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
  103 |      res=find_centroids(u, total);
      |                                 ^
race.cpp:88:21: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
   88 |         return {u, s};
      |                     ^

• Subtask 1: 0 / 9
• Subtask 2: 0 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57