Submission #413673

#	Time	Username	Problem	Language	Result	Execution time	Memory
413673		Mahmudul_Kabir	Race (IOI11_race)	C++14	21 / 100	3066 ms	14204 KiB

race

#include "race.h"

#include <bits/stdc++.h>

#define sp <<" "
#define el <<"\n"
#define S second
#define F first
#define pb push_back
#define all(ar) ar.begin(),ar.end()
#define pii pair<int,int>


using namespace std;
using ll = long long;
using ld = long double;

const int mxr = 200005;
const int big = 2000000999;

int n,k,ans = big;
vector<vector<pii>> g;
bitset<mxr> ded;

void dfs(int v,int p,vector<int> &sz){
  sz[v] = 1;
  for(pii r: g[v]){
    if(r.F == p || ded[r.F]) continue; 
    dfs(r.F,v,sz); 
    sz[v] += sz[r.F]; 
  }
  return; 
}

int fcen(int v,int p,int lim,vector<int> &sz){
  for(pii r: g[v]){
    if(r.F == p || ded[r.F]) continue;
    if(sz[r.F] > lim) return fcen(r.F,v,lim,sz);
  }
  return v;
}

void fil(int v,int p,int cost,int dep,unordered_map<int,int> &dis,unordered_map<int,int> &cum){
  if(cost > k) return;
  if(cum.count(k - cost)) ans = min(ans, dep + cum[k - cost]);  
  dis[cost] = dis.count(cost) ? min(dis[cost],dep) : dep; 
  for(pii r: g[v]){
    if(r.F == p || ded[r.F]) continue;
    fil(r.F,v,cost + r.S,dep+1,dis,cum);
  }
  return;
}

void decompose(int v){
  vector<int> sz(n+1);
  dfs(v,-1,sz);
  int lim = (sz[v]/2);
  int cen = fcen(v,-1,lim,sz);  
  ded[cen] = 1;
  unordered_map<int,int> cum;  
  for(pii r: g[cen]){
    if(ded[r.F]) continue; 
    unordered_map<int,int> dis; 
    fil(r.F,cen,r.S,1,dis,cum);
    for(pii x: dis) cum[x.F] = cum.count(x.F) ? min(cum[x.F],x.S) : x.S; 
  } 
  if(cum.count(k)) ans = min(ans,cum[k]);  
  for(pii r: g[cen]){
    if(!ded[r.F]) decompose(r.F);
  }
}

int best_path(int N, int K, int H[][2], int L[])
{
  n = N;
  k = K;
  g.assign(n,{});
  for(int i = 1; i < n; i++){
    int a = H[i-1][0], b = H[i-1][1], c = L[i-1]; 
    g[a].pb({b,c});
    g[b].pb({a,c});
  } 
  decompose(0);
  return ans == big ? -1 : ans;
}

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