Submission #680538

#	Time	Username	Problem	Language	Result	Execution time	Memory
680538		tommy1024	Race (IOI11_race)	C++17	0 / 100	4 ms	5076 KiB

race

#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#define pii pair<int,int>
using namespace std;
typedef long long ll;
const int inf=1e9;
int N,K;
int a,b,c;
int sz[200005],kill[200005];
int ans=inf;
vector <pii> v[200005];
map <int,int> m,tmp;
int get_sz(int x,int par){
    sz[x]=1; // reset
    for(auto[i,d]:v[x]){
        if(i==par)continue;
        if(kill[i])continue;
        sz[x]+=get_sz(i,x);
    }
    return sz[x];
}
int get_cent(int x,int par,int c){
    for(auto[i,d]:v[x]){
        if(i==par)continue;
        if(kill[i])continue;
        if(sz[i]>c)return get_cent(i,x,c);
    }
    return x;
}
void sch(int x,int d,int st,int tab){ // step
    if(d>K)return;
    auto it=tmp.find(d);
    if(it==tmp.end())tmp[d]=st;
    else tmp[d]=min(tmp[d],st);
    for(auto[i,D]:v[x]){
        if(i==tab)continue;
        if(kill[i])continue;
        sch(i,d+D,st+1,x);
    }
}
void update(){
    for(auto[a,b]:tmp){
        auto it=m.find(a);
        if(it==m.end())m[a]=b;
        else m[a]=min(m[a],b);
    }
}
void f(int x){
    int s=get_sz(x,-1); // already considered in kill[]
    int ct=get_cent(x,-1,s/2);
    kill[ct]=1;
    for(auto[i,d]:v[ct]){
        if(kill[i]){
            continue;
        }
        tmp.clear();tmp[0]=0;
        sch(i,d,1,x);
        for(auto[a,b]:tmp){
            if(a>K)continue;
            auto it=m.find(K-a);
            if(it!=m.end()){
                ans=min(ans,m[K-a]+b);
                //printf("[%d %d]",m[K-a],b);
            }
        }
        update();
    }
    m.clear();
    m[0]=0;
    for(auto[i,d]:v[ct]){
        if(kill[i])continue;
        f(i);
    }
}
int best_path(int n,int k,int h[][2],int l[]){
    N=n,K=k;
    for(int i=0;i<N-1;i++){
        a=h[i][0],b=h[i][1];
        c=l[i];
        v[a].push_back({b,c});
        v[b].push_back({a,c});
    }
    m[0]=0;
    f(0);
    if(ans==inf)ans=-1;
    return ans;
}

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