Submission #1162478

#	Time	Username	Problem	Language	Result	Execution time	Memory
1162478		brinton	Road Closures (APIO21_roads)	C++20	24 / 100	2095 ms	21832 KiB

roads

#include "roads.h"

#include <bits/stdc++.h>
using namespace std;
int k;
vector<vector<pair<int,int>>> edges;
pair<long long,long long> dfs(int cur,int par){
  vector<pair<long long,long long>> child;// not delete parent, delete parent

  for(auto [nxt,w]:edges[cur]){
    if(nxt == par)continue;
    auto [np,cp] = dfs(nxt,cur);
    np = min(np,cp+w);
    child.push_back({np,cp+w});
  }
  long long base = 0;
  vector<long long> diff;
  for(auto [np,cp]:child){
    base += np;
    diff.push_back(cp-np);
  }
  sort(diff.begin(),diff.end());
  int out = 1+child.size();
  int del = out-k;// k must greater than 1
  pair<long long,long long> result;// not delete parent, delete parent

  long long ndelp = base,delp = base;
  // ndel parent, (all del on child)
  for(int i = 0;i < del;i++){
    ndelp += diff[i];
  }
  // not chose p, 
  for(int i = 0;i < del-1;i++){
    delp += diff[i];
  }
  return {ndelp,delp};
  // greedy;
}
vector<long long> minimum_closure_costs(int N, vector<int> U,vector<int> V,vector<int> W) {
  // N^2 solution
  vector<long long> ans(N,0);
  edges.resize(N);
  for(int i = 0;i < N-1;i++){
    edges[U[i]].push_back({V[i],W[i]});
    edges[V[i]].push_back({U[i],W[i]});
  }
  for(auto i:W) ans[0] += i;
  for(int i = 1;i <= N-1;i++){
    k = i;
    pair<long long,long long> res = dfs(0,-1);
    ans[i] = min(res.first,res.second);
  }
  return ans;
}

// // grader
// #include "roads.h"

// #include <cassert>
// #include <cstdio>

// #include <vector>

// int main() {
//   int N;
//   assert(1 == scanf("%d", &N));

//   std::vector<int> U(N - 1), V(N - 1), W(N - 1);
//   for (int i = 0; i < N - 1; ++i) {
//     assert(3 == scanf("%d %d %d", &U[i], &V[i], &W[i]));
//   }

//   std::vector<long long> closure_costs = minimum_closure_costs(N, U, V, W);
//   for (int i = 0; i < static_cast<int>(closure_costs.size()); ++i) {
//     if (i > 0) {
//       printf(" ");
//     }
//     printf("%lld",closure_costs[i]);
//   }
//   printf("\n");
//   return 0;
// }

• Subtask 1: 0 / 5
• Subtask 2: 0 / 7
• Subtask 3: 14 / 14
• Subtask 4: 10 / 10
• Subtask 5: 0 / 17
• Subtask 6: 0 / 25
• Subtask 7: 0 / 22