Submission #764069

#	Time	Username	Problem	Language	Result	Execution time	Memory
764069		Ryuga_	Race (IOI11_race)	C++14	0 / 100	3 ms	4948 KiB

race

#include <bits/stdc++.h>
#include <bits/extc++.h>

using namespace std;



#define F first 
#define S second 

const int N = 2e5 + 10;
int sub[N] , process[N];
vector<pair<int,int>>g[N];
int ans = INT_MAX;
map<int,int>mp;
int n , k;
int dfs(int u , int p)
{
        sub[u] = 1;
        for(auto v : g[u]){
                if(v.F != p && !process[v.F]){
                        sub[u] += dfs(v.F,u);
                }
        }

        return sub[u];
}


int centroid(int u , int p , int req)
{
        for(auto v : g[u]){
                int x = v.F;
                if(x != p && !process[x] && sub[x] >= req){
                        return centroid(x,u,req);
                }
        }

        return u;
}


void f(int u , int p , int keep, int level,int depth)
{
        if(depth > k)return;
        if(!keep){
                if(mp.find(k-depth) != mp.end()){
                        ans = min(ans,level+mp[k-depth]);
                }
        }

        else{
                if(mp.find(k-depth) != mp.end()){
                        mp[depth] = min(mp[depth],level);
                }
                else mp[depth] = level;
        }

        for(auto v : g[u]){
                if(v.F != p && !process[v.F]){
                        f(v.F,u,keep,level+1,depth+v.S);
                }
        }
}
void decompos(int u)
{
        int x = dfs(u,-1);
        int cen = centroid(u,-1,x/2);
        process[cen] = 1;
        
        mp[0] = 0;
        for(auto v : g[cen]){
                if(!process[v.F]){
                        f(v.F,cen,0,1,v.S);
                        f(v.F,cen,1,1,v.S);
                }
        }

        mp.clear();
        for(auto v : g[cen]){
                if(!process[v.F]) decompos(v.F);
        }
}

int  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] , y = H[i][1] , w = L[i];
                g[x].push_back({y,w});
                g[y].push_back({x,w});
        }
        decompos(0);
        if(ans == INT_MAX) ans = -1;
        return ans;
}

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