Submission #41020

#	Time	Username	Problem	Language	Result	Execution time	Memory
41020		Hassoony	Race (IOI11_race)	C++14	100 / 100	2125 ms	58484 KiB

race

#include<bits/stdc++.h>
#include<unordered_map>
using namespace std;
typedef double D;
typedef long long ll;
const ll mod=1e9+7;
const ll inf=(1ll<<62);
const int SQ=400;
const int MX=2e5+9;
int n,a,b,subtree[MX],blocked[MX],par[MX],depth[MX],k,dis[MX];
vector<pair<int,int> >v[MX];
vector<int>f;
ll ans=0;
unordered_map<int,int>cnt;
void dfs_size(int x,int p){
    subtree[x]=1;par[x]=p;
    for(auto pp:v[x]){
        if(pp.first==p||blocked[pp.first])continue;
        dfs_size(pp.first,x);
        subtree[x]+=subtree[pp.first];
    }
}
vector<int>nodes;
void DFS(int x,int p,int sum){
    if(sum>k)return;
    f.push_back(x);
    nodes.push_back(x);
    dis[x]=sum;
    for(auto pp:v[x]){
        if(pp.first==p||blocked[pp.first])continue;
        depth[pp.first]=depth[x]+1;
        DFS(pp.first,x,sum+pp.second);
    }
}
void create(int x){
    dfs_size(x,-1);
    int S=subtree[x],idx;
    queue<int>q;
    q.push(x);
    while(!q.empty()){
        int nxt=q.front();q.pop();
        int s=subtree[x]-subtree[nxt];
        for(auto pp:v[nxt]){
            if(pp.first==par[nxt]||blocked[pp.first])continue;
            s=max(s,subtree[pp.first]);
            q.push(pp.first);
        }
        if(S>s){
            S=s;
            idx=nxt;
        }
    }
    for(auto pp:f){
        cnt[dis[pp]]=0;
        dis[pp]=depth[pp]=0;
    }
    f.clear();
    blocked[idx]=1;
    cnt[0]=0;
    dis[idx]=depth[idx]=0;
    for(auto pp:v[idx]){
        if(blocked[pp.first])continue;
        depth[pp.first]=1;
        DFS(pp.first,idx,pp.second);
        for(auto nxt:nodes){
            if(k-dis[nxt]<0)continue;
            if(dis[nxt]==k)ans=min(ans,(ll)depth[nxt]);
            if(cnt[k-dis[nxt]]==0)continue;
            ans=min(ans,(ll)depth[nxt]+cnt[k-dis[nxt]]);
        }
        for(auto i:nodes){
            if(cnt[dis[i]]==0){cnt[dis[i]]=depth[i];}
            else cnt[dis[i]]=min(cnt[dis[i]],depth[i]);
        }
        nodes.clear();
    }
   // cout<<"answer: "<<ans<<endl;
    for(auto pp:v[idx]){
        if(blocked[pp.first])continue;
        create(pp.first);
    }
}
int c;
ll best_path(int N,int K,int H[][2],int L[]) {
    n=N,k=K;
    for(int i=0;i<n-1;i++) {
        int x=H[i][0]+1,y=H[i][1]+1,w=L[i];
        v[x].push_back({y,w});
        v[y].push_back({x,w});
    }
    ans=inf;
    create(1);
    if(ans==inf)return -1;
    return ans;
}

Compilation message (stderr)

race.cpp: In function 'void create(int)':
race.cpp:37:22: warning: 'idx' may be used uninitialized in this function [-Wmaybe-uninitialized]
     int S=subtree[x],idx;
                      ^~~

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