Submission #339216

#	Time	Username	Problem	Language	Result	Execution time	Memory
339216		bigDuck	Race (IOI11_race)	C++14	9 / 100	1822 ms	16236 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 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;
}



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

            int mx=0, u=s;
        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[s])>mx)  ){
                mx=total-sz[s]; u=node.ft;
            }
        }
    int res;
    if(v[u]){res=s;}
    else{
        res=find_centroid(u, total);
    }
    v[s]=false;
    return res;
}



int k1[1000010];



void path(int s, int l, int h){

v[s]=true;


if((k1[k-l]>0) ){
    res=min(res, h+k1[k-l]-1);
}

for(pii pr:g[s]){
    int u=pr.ft, d=pr.sc;
    if( (!v[u]) && ( (l+d)<=(k) ) ){
        path(u, l+d, h+1);
    }
}

if(k1[l]==0){
    k1[l]=h;
}
else{
    k1[l]=min(k1[l], h);
}

v[s]=false;
return ;
}

queue<int> forest;
void remove_path(int s, int l, int c){

v[s]=true;
k1[l]=0;
for(int i=g[s].size()-1; i>=0; i--){
        pii pr=g[s][i];

    int u=pr.ft, d=pr.sc;

    if(s==c){
        g[s].pop_back();
        g[u].erase(find(g[u].begin(), g[u].end(), mp(s, d) ) );
        forest.push(u);
    }

    if( (!v[u]) && ( (l+d)<=(k) ) ){
        remove_path(u, l+d, c);
    }
}
v[s]=false;
return ;

}








void subtask_4(){

forest.push(1);

while(!forest.empty()){
    int node=forest.front(); forest.pop();
    build_sz(node);
    if(sz[node]==1){continue;}
    int c=find_centroid(node, sz[node]);
    //cout<<c<<"\n"<<flush;
    k1[0]=1;
    path(c, 0, 1);
    remove_path(c, 0, c);
}


}








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});
  }



    subtask_4();
  if(res==(1e9)){
    return -1;
  }
  return res-1;
}

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