Submission #986821

#	Time	Username	Problem	Language	Result	Execution time	Memory
986821		huutuan	Race (IOI11_race)	C++14	43 / 100	307 ms	68076 KiB

race

#include "race.h"

#include <bits/stdc++.h>

using namespace std;

#define int long long

const int N=2e5+10, M=1e6+10, inf=1e9;
int n, k, tin[N], tout[N], tdfs, tour[N];
vector<pair<int, int>> g[N];
int dep[N], dist[N], sz[N];
map<int, int> mp;
int ans;

void dfs_sz(int u, int p){
   tin[u]=++tdfs;
   tour[tdfs]=u;
   for (int i=0; i<(int)g[u].size(); ++i){
      if (g[u][i].first==p){
         g[u].erase(g[u].begin()+i);
         break;
      }
   }
   sz[u]=1;
   for (auto &e:g[u]){
      int v=e.first, w=e.second;
      dep[v]=dep[u]+1;
      dist[v]=dist[u]+w;
      dfs_sz(v, u);
      sz[u]+=sz[v];
      if (sz[v]>sz[g[u][0].first]) swap(e, g[u][0]);
   }
   tout[u]=tdfs;
}

void minimize(int x, int y){
   auto it=mp.find(x);
   if (it==mp.end()) mp[x]=y;
   else it->second=y;
}

int get(int x){
   auto it=mp.find(x);
   if (it==mp.end()) return inf;
   return it->second;
}

void dfs_merge(int u, bool keep){
   if (g[u].empty()){
      if (keep) minimize(dist[u], dep[u]);
      return;
   }
   for (auto &e:g[u]) if (e!=g[u][0]) dfs_merge(e.first, 0);
   dfs_merge(g[u][0].first, 1);
   for (auto &e:g[u]) if (e!=g[u][0]){
      int v=e.first;
      for (int i=tin[v]; i<=tout[v]; ++i){
         int w=tour[i];
         ans=min(ans, get(k-dist[w]+dist[u]*2)+dep[w]-dep[u]*2);
      }
      for (int i=tin[v]; i<=tout[v]; ++i){
         int w=tour[i];
         minimize(dist[w], dep[w]);
      }
   }
   ans=min(ans, get(k+dist[u])-dep[u]);
   minimize(dist[u], dep[u]);
   if (!keep) mp.clear();
}

int32_t best_path(int32_t _N, int32_t K, int32_t H[][2], int32_t L[])
{
   n=_N, k=K;
   for (int i=0; i<n-1; ++i){
      int u=H[i][0]+1, v=H[i][1]+1, w=L[i];
      g[u].emplace_back(v, w);
      g[v].emplace_back(u, w);
   }
   dfs_sz(1, 0);
   ans=inf;
   dfs_merge(1, 0);
   return ans>n?-1:ans;
}

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