Submission #230002

#	Time	Username	Problem	Language	Result	Execution time	Memory
230002		DavidDamian	Race (IOI11_race)	C++11	0 / 100	7 ms	5120 KiB

race

//#include "race.h"
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define debug(x) cout<<#x<<" = "<<x<<endl
struct edge
{
    int to;
    int w;
};
int blocked[200005];
vector<edge> adjList[200005];
int subtree_size[200005];
void computeSize(int u,int p)
{
    subtree_size[u]=1;
    for(edge e: adjList[u]){
        int v=e.to;
        if(blocked[v] || v==p) continue;
        computeSize(v,u);
        subtree_size[u]+=subtree_size[v];
    }
}
int findCentroid(int root)
{
    computeSize(root,-1);
    int n=subtree_size[root];
    int u=root;
    bool found=false;
    do{
        found=true;
        for(edge e: adjList[u]){
            int v=e.to;
            if(blocked[v]) continue;
            if(subtree_size[v]>n/2){
                found=false;
                subtree_size[u]-=subtree_size[v];
                subtree_size[v]+=subtree_size[u];
                u=v;
                break;
            }
        }
    }while(!found);
    return u;
}
int k;
int minimum=INT_MAX;
void dfs(int u,int p,int distRoot,int depth,map<int, multiset<int> >& dist)
{
    if(distRoot>k)
        return;
    dist[distRoot].insert(depth);
    for(edge e: adjList[u]){
        int v=e.to;
        if(blocked[v] || v==p) continue;
        dfs(v,u,distRoot+e.w,depth+1,dist);
    }
}
typedef pair<int, multiset<int> > pii;
void decompose(int root)
{
    int centroid=findCentroid(root);
    map<int, multiset<int> > dist;
    dfs(centroid,-1,0,0,dist);
    if(dist[k].size()>0 && *(dist[k].begin())>0)
        minimum=min(minimum,*(dist[k].begin()));
    for(pii x: dist){
        if(k%2==0 && x.first==k/2){ //Special case
            int i=0;
            int value=0;
            for(int edges: x.second){
                if(i==2) break;
                value+=edges;
                i++;
            }
            if(i==2) minimum=min(minimum,value);
            continue;
        }
        if(x.second.size()==0 || dist[abs(k-x.first)].size()==0) continue;
        int value_1=*(x.second.begin());
        int value_2=*(dist[abs(k-x.first)].begin());
        if(value_1!=0 && value_2!=0)
            minimum=min(minimum,value_1+value_2);
    }
    dist.clear();
    blocked[centroid]=1;
    for(edge e: adjList[centroid]){
        int v=e.to;
        if(blocked[v]) continue;
        decompose(v);
    }
}
int best_path(int n, int K, int H[][2], int L[])
{
    k=K;
    for(int i=0;i<n-1;i++){
        int a=H[i][0];
        int b=H[i][1];
        int w=L[i];
        adjList[a].push_back({b,w});
        adjList[b].push_back({a,w});
    }
    decompose(0);
    return (minimum!=INT_MAX)? minimum : -1;
}

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