Submission #1149040

#	Time	Username	Problem	Language	Result	Execution time	Memory
1149040		sasde	Race (IOI11_race)	C++20	0 / 100	10 ms	23872 KiB

race

#include<bits/stdc++.h>
#define str string
#define task "strdel"
#define ii pair<int,int>
#define iii pair<int,ii>
#define iv pair<ii,ii>
#define se second
#define fi first
#define ffi fi.fi
#define sfi se.fi
#define sse se.se
#define fse fi.se
#define lt(i, c, d) for(int i = c; i <= d; ++i)
#define fl(i, c, d) for(int i = d; i >= c; --i)
#define pb push_back
#define emb emplace_back
#define emf emplace_front
#define em emplace
using namespace std;
const int N=1e6+5,lg=20,mod=1e9+7;
mt19937 rd(chrono::steady_clock::now().time_since_epoch().count());
int Rand(int u,int v){
 return u+rd()%(v-u+1);
}
int n,k,sz[N],dp[N],ans=1e9;
vector<ii>a[N];
bool check[N];
void dfs(int u,int cha){
  sz[u]=1;
  for(ii v:a[u]){
    if(v.fi==cha||check[v.fi])continue;
    dfs(v.fi,u);
    sz[u]+=sz[v.fi];
  }
}
int fin(int u,int cha,int n){

  for(ii v:a[u]){
    if(v.fi!=cha&&!check[v.fi]&&sz[v.fi]>n/2)return fin(v.fi,u,n);
  }
  return u;
}
void add(int u,int cha,int sum,int canh){
  // cout <<u<<" "<<canh<<" "<<sum<<" "<<dp[sum]<<'\n';
  ans=min(ans,canh+dp[k-sum]);
  for(ii v:a[u]){
    if(v.fi==cha||check[v.fi]||sum-v.se<0)continue;
    add(v.fi,u,sum-v.se,canh+1);
  }
}
stack<int>s;
void them(int u,int cha,int sum,int canh){
  dp[sum]=min(dp[sum],canh);
  s.push(sum);
  for(ii v:a[u]){
    if(v.fi==cha||check[v.fi]||sum-v.se<0)continue;
    them(v.fi,u,sum-v.se,canh+1);
  }
}
void buildcen(int u,int cha){
  dfs(u,-1);
  int g=fin(u,-1,sz[u]);
  // cout <<g<<'\n';
  // for(int i=1;i<=n;++i)cout <<sz[i]<<" ";
  check[g]=true;
  for(ii v:a[g]){
    if(v.fi==cha||check[v.fi]||k-v.se<0)continue;
    add(v.fi,g,k-v.se,1);
    them(v.fi,g,k-v.se,1);
  }
  while(!s.empty()){
    // cout <<g<<" "<<s.top()<<'\n';
    dp[s.top()]=1e9;
    s.pop();
  }
  for(ii v:a[g]){
    if(v.fi==cha||check[v.fi])continue;
    buildcen(v.fi,g);
  }
}

int best_path(int n,int k,int b[][2],int w[]){
  // for(int i=1;i<n;++i)cin >> b[i][1] >> b[i][0];
    // for(int i=1;i<n;++i)cin >> w[i];
  for(int i=1;i<n;++i){
    int u=b[i][1]+1,v=b[i][0]+1;
    // cout <<u<<" "<<v<<" "<<w<<'\n';
    a[u].emb(v,w[i]);
    a[v].emb(u,w[i]);
  }
  for(int i=1;i<=k;++i)dp[i]=1e9;
  buildcen(1,-1);

  cout<< (ans==1e9?-1:ans);
}

Compilation message (stderr)

race.cpp: In function 'int best_path(int, int, int (*)[2], int*)':
race.cpp:95:1: warning: no return statement in function returning non-void [-Wreturn-type]
   95 | }
      | ^

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