Submission #649900

#	Time	Username	Problem	Language	Result	Execution time	Memory
649900		KoalaMuch	Race (IOI11_race)	C++14	0 / 100	4 ms	5076 KiB

race

#include "race.h"
#include<iostream>
#include<utility>
#include<vector>
#include<map>
using namespace std;
const int N = 2e5+5;
int sz[N];
int st[N];
int ft[N];
int ver[N];
int orig_len[N];
int orig_sum[N];
map<int,int> mem;
vector<pair<int,int>> g[N];
int t;
int ans = 1e9;
void preprocess(int u,int len=0,int sum=0,int p = -1){
    ++t;
    st[u] = t;
    ver[t] = u;
    orig_sum[u] = sum;
    orig_len[u] = len;
    sz[u] = 1;
    for(auto &x:g[u]){
        if(x.first!=p){
            preprocess(x.first,len+1,sum+x.second,u);
            sz[u]+=sz[x.first];
        }
    }
    ft[u] = t;
}
void solve(int u,int target,int p = -1,bool keep = false){
    int mx = -1,big_child = -1,del_sum = orig_sum[u],del_len = orig_len[u];
    for(auto &x:g[u])   if(x.first!=p&&sz[x.first]>mx)  mx = sz[x.first],big_child = x.first;
    for(auto &x:g[u]){
        if(x.first!=p&&x.first!=big_child){
            solve(x.first,target,u,false);
        }
    }
    if(big_child!=-1){
        solve(big_child,target,u,true);
    }
    int need = target-orig_sum[u]+2*del_sum;
    if(need>=0&&need<=1000000&&mem[need])  ans = min(ans,mem[need]+orig_len[u]-2*del_len);
    if(!mem[orig_sum[u]])   mem[orig_sum[u]] = orig_len[u];
    mem[orig_sum[u]] = min(mem[orig_sum[u]],orig_len[u]);
    for(auto &x:g[u]){
        if(x.first!=p&&x.first!=big_child){
            for(int i=st[x.first];i<=ft[x.first];i++){
                int v = ver[i];
                need = target-orig_sum[v]+2*del_sum;
                if(need>=0&&need<=1000000&&mem[need])  ans = min(ans,mem[need]+orig_len[v]-2*del_len);
                if(!mem[orig_sum[v]])   mem[orig_sum[v]] = orig_len[v];
                mem[orig_sum[v]] = min(mem[orig_sum[v]],orig_len[v]);
            }
        }
    }
    if(!keep){
        for(int i=st[u];i<=ft[u];i++){
            mem.erase(orig_sum[ver[i]]);
        }
    }
}
int best_path(int N, int K, int H[][2], int L[])
{
  for(int i=0;i<N;i++)  g[H[i][0]].push_back({H[i][1],L[i]}),g[H[i][1]].push_back({H[i][0],L[i]});
  preprocess(0);
  solve(0,K);
  if(ans>=N)  return -1;
  return ans;
}

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