Submission #777426

#	Time	Username	Problem	Language	Result	Execution time	Memory
777426		a_aguilo	Race (IOI11_race)	C++14	21 / 100	3077 ms	14672 KiB

race

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

using namespace std;

int n, k;
const int maxN = 200000;
vector<pair<int, int>> AdjList[maxN];
vector<int> exists;
int padre[maxN];
int subTreeSize[maxN];
unordered_map<int, int> M;

void print(vector<pair<int, int>>& V){
  for(pair<int, int>& pii: V){
    cout << pii.first << " ";
  }
  cout << endl;
}

void preProcess(int node){
  subTreeSize[node] = 1;
  for(pair<int, int>& next: AdjList[node]){
    //cout << node << " -> " << next.first << endl;
    if(next.first != padre[node] && exists[next.first]){
      padre[next.first] = node;
      preProcess(next.first);
      subTreeSize[node] += subTreeSize[next.first];
    }
  }
  //cout << node << " " << subTreeSize[node] << endl;
}

int find_Centroid(int node, int sze){
  for(pair<int, int>& next: AdjList[node]){
    if(next.first == padre[node] || !exists[next.first]) continue;
    if(subTreeSize[next.first] > (sze/2)) return find_Centroid(next.first, sze);
  }
  return node;
}

void findDistances(int node, int currDist, int numEdges, vector<pair<int, int>>& V){
  if(currDist > k) return;
  V.push_back({currDist, numEdges});
  for(pair<int, int>& next: AdjList[node]){
    if(exists[next.first] && next.first != padre[node]){
      padre[next.first] = node;
      findDistances(next.first, currDist+next.second, numEdges+1, V);
    }
  }
}

int solveSubTree(int node){
  padre[node] = node;
  preProcess(node);
  int sze = subTreeSize[node];
  node = find_Centroid(node, sze);
  //cout << node << endl;
  padre[node] = node;

  M.clear();
  int ans = 1e9;

  for(pair<int, int>& next: AdjList[node]){
    if(next.first == padre[node]) continue;
    if(!exists[next.first]) continue;
    padre[next.first] = node;
    vector<pair<int, int>> prov;
    findDistances(next.first, next.second, 1, prov);
    for(pair<int, int>& val: prov){
      int d = val.first;
      int edges = val.second;
      if(M.find(k-d) != M.end())ans = min(ans, M[k - d] + edges);
    }
    for(pair<int, int>& val: prov){
      int d = val.first;
      int edges = val.second;
      if(M.find(d) == M.end()) M[d] = edges;
      else M[d] = min(M[d], edges);
    }
    /*
    cout << node << " -> " << next.first << endl;
    for(int i = 1; i <= k; ++i) cout << lengths[i] << " ";
    cout << endl;*/
  }
  if(M.find(k) != M.end())ans = min(ans, M[k]);

  exists[node] = 0;

  for(pair<int, int>& next: AdjList[node]){
    if(exists[next.first]) ans = min(ans, solveSubTree(next.first));
  }
  return ans;
}

int best_path(int N, int K, int H[][2], int L[])
{
  n = N;
  k = K;
  exists = vector<int>(N, 1);
  M.reserve(262144);
  int a, b, c;
  for(int i = 0; i < N-1; ++i){
    a = H[i][0];
    b = H[i][1];
    c = L[i];
    AdjList[a].push_back({b, c});
    AdjList[b].push_back({a, c});
  }
  /*
  for(int i = 0; i < N-1; ++i){
    cout << i << '\t';
    print(AdjList[i]);
  }*/
  int res = solveSubTree(0);
  if(res == 1e9) return -1;
  return res;
}

/*
int main(){
  int N, K;
  cin >> N >> K;
  int H[N-1][2];
  int L[N-1];
  for(int i = 0; i < N-1; ++i) cin >> H[i][0] >> H[i][1] >> L[i];
  cout << best_path(N, K, H, L);
  return 0;
}*/

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