Submission #802747

#	Time	Username	Problem	Language	Result	Execution time	Memory
802747		ashcomp	LOSTIKS (INOI20_lostiks)	C++14	0 / 100	241 ms	185052 KiB

Main

#include <bits/stdc++.h>
 
using namespace std;
 
#define all(x) x.begin() , x.end()
#define pii pair<int,int>
#define pll pair<ll,ll>
#define F first
#define S second
#define wall cerr<<"------------------------"<<endl
 
typedef long long ll;
 
const ll INF = 1e18;
const ll maxn = 1e6 + 10;
const ll mod = 1e9 + 7;
 
int n , m , k , ST , EN;
int h[maxn] , p[maxn] , st[maxn] , en[maxn];
int a[maxn<<1] , rmq[maxn<<1][21] , ps_rmq[maxn<<1][21] , rrmq[maxn<<1][21] , ps_rrmq[maxn<<1][21] , len[maxn<<1];
vector<int> g[maxn] , LSA;
bool mrk[maxn];
 
void DFS(int v)
{
        mrk[v] = 1;
        LSA.push_back(v);
        st[v] = LSA.size()-1;
        for(auto u : g[v]){
 
                if(mrk[u]==1)continue;
                p[u] = v;
                h[u] = h[v]+1;
                DFS(u);
                LSA.push_back(v);
        }
        en[v] = LSA.size()-1;
        
}
void pre_LCA()
{
        LSA.push_back(0);
        p[ST] = -1;
        h[ST] = 1;
        DFS(ST);
        m = LSA.size()-1;
        //wall;
        for(int i=1; i<=m; i++){
                a[i] = h[LSA[i]];
        }
        for(int j=0; j<21; j++){
                for(int i=1; i<=m; i++){
                        if(j==0){
                                rmq[i][j] = a[i];
                                rrmq[i][j] = a[i];
                                ps_rmq[i][j] = i;
                                ps_rrmq[i][j] = i;
                                continue;
                        }
                        if((i+(1<<j)-1)<=m){
                                rmq[i][j] = rmq[i][j-1];
                                ps_rmq[i][j] = ps_rmq[i][j-1];
                                if(rmq[i][j-1] > rmq[i+(1<<(j-1))][j-1]){
                                        rmq[i][j] = rmq[i+(1<<(j-1))][j-1];
                                        ps_rmq[i][j] = ps_rmq[i+(1<<(j-1))][j-1];
                                }
                        }
                        if((i-(1<<j)+1)>0){
                                rrmq[i][j] = rrmq[i][j-1];
                                ps_rrmq[i][j] = ps_rrmq[i][j-1];
                                if(rrmq[i][j-1] > rrmq[i-(1<<(j-1))][j-1]){
                                        rrmq[i][j] = rrmq[i-(1<<(j-1))][j-1];
                                        ps_rrmq[i][j] = ps_rrmq[i-(1<<(j-1))][j-1];
                                }
                        }
                }
        }
        int PS = 0;
        for(int i=1; i<=m; i++){
                if(((1<<PS)<<1)<=i){
                        PS++;
                }
                len[i] = PS;
        }
}//OK
int LCA(int v , int u)
{
        int l = min(st[v],st[u]) , r=max(st[v],st[u]);
        int ln = len[r-l+1];
        int x = rmq[l][ln] , y = rrmq[r][ln];
        if(x < y){
                int pos = ps_rmq[l][ln];
                return LSA[pos];
        }else{
                int pos = ps_rrmq[r][ln];
                return LSA[pos];
        }
}
 
int times=0;
map<int,bool> mp[maxn];
vector<int> ORDER;
vector<pii> eg[maxn];
int dfs(int v , int tm , int end)
{
        //cout<<v<<"=>"<<end<<" : "<<end<<"\n";
        if(times>20){
                return -1;
        }
        if(v==end){
                return 1;
        }
        for(auto e : eg[v]){
                int u=e.F , w=e.S;
                int now = h[end]+h[v]-h[LCA(end,v)]-h[LCA(end,v)];
                int then = h[end]+h[u]-h[LCA(end,u)]-h[LCA(end,u)];
                if(then < now){
                        if(mp[v][u]==0){
                                times++;
                                int tp = dfs(v,times,w);
                                if(tp==-1){
                                        return -1;
                                }
                                ORDER.push_back(w);
                                ORDER.push_back(v);
                                mp[v][u] = 1;
                                mp[u][v] = 1;
                                tp = dfs(u,tm,end);
                                if(tp==-1)return -1;
                        }else{
                                int tp = dfs(u,tm,end);
                                if(tp==-1)return -1;
                        }
                        
                }
        }
        return 1;
}
 
int main()
{
        ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL);
        cin>>n>>ST>>EN;

        for(int i=1; i<n; i++){
                int v,u,w; cin>>v>>u>>w;
                if(w==0){
                        mp[v][u] = 1;
                        mp[u][v] = 1;
                }
                eg[v].push_back({u,w});
                eg[u].push_back({v,w});
                g[v].push_back(u);
                g[u].push_back(v);
        }
        pre_LCA();
        ORDER.push_back(ST);
        int tp = dfs(ST,1,EN);
        ORDER.push_back(EN);
        if(tp==-1){
                cout<<"-1"<<endl;
        }else{
                ll ans = 0 , sz=ORDER.size();
                for(int i=1; i<sz; i++){
                        int v = ORDER[i-1] , u=ORDER[i];
                        ans += h[v]+h[u]-h[LCA(v,u)]-h[LCA(v,u)]; 
                }
                cout<<ans;
        }
        return 0;
}
/*
6
1 6
1 2 0
2 3 0
2 4 5
2 5 3
5 6 4
ans = 14;
*/
/**
4
1 4
1 2 0
1 3 2
3 4 1
ans = 4;
*/
/*
5
3 1
1 2 5
2 3 4
3 4 0
4 5 2
ans = 10;
*/

• Subtask 1: 0 / 23
• Subtask 2: 0 / 36
• Subtask 3: 0 / 41