Submission #806749

#	Time	Username	Problem	Language	Result	Execution time	Memory
806749		ashcomp	LOSTIKS (INOI20_lostiks)	C++14	23 / 100	2080 ms	279764 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 = 1e9;
const ll maxn = 2e6 + 10;
const ll mod = 1e9 + 7;
 
int n , m , k , ST , EN , ti;
int h[maxn] , p[maxn] , st[maxn] , en[maxn];
int a[maxn<<1] , par[maxn<<1][22] , len[maxn<<1];
vector<int> g[maxn] , LSA;
bool mrk[maxn];
void DFS(int v)
{
        mrk[v] = 1;
        st[v] = ti++;
        for(auto u : g[v]){
                if(mrk[u]==1)continue;
                p[u] = v;
                h[u] = h[v]+1;
                DFS(u);
        }
        en[v] = ti++;
}
inline void pre_LCA()
{
        p[ST] = ST;
        DFS(ST);
        for(int j=0; j<21; j++){
                for(int i=1; i<=n; i++){
                        if(j==0){
                                par[i][j] = p[i];
                                continue;
                        }else{
                                int x = par[i][j-1];
                                par[i][j] = par[x][j-1];
                        }
                }
        }
}//OK
inline int LCA(int v , int u)
{
        if(st[v]<=st[u]&&en[u]<=en[v])return v;
        if(st[u]<=st[v]&&en[v]<=en[u])return u;
        for(int i=20; i>=0; i--){
                int x = par[v][i];
                if(st[x]>=st[u] || en[u]>=en[x]){
                        v = x;
                }
        }
        v = p[v];
        return v;
}
inline int DIS(int v , int u)
{
        return (h[v]+h[u]-h[LCA(v,u)]-h[LCA(v,u)]);
}
 
vector<pii> eg[maxn];
bool mark[maxn];
int req[maxn];
map<int,int> MP[maxn]; 
void dfs(int v)
{
        mark[v] = 1;
        for(auto e : eg[v]){
                int u=e.F , w=e.S;
                if(mark[u]==1)continue;
                p[u] = v;
                req[u] = req[v];
                if(w!=0){
                        int x = MP[v][u];
                        req[u] |= (1<<x);
                }
                dfs(u);
        }
}
 
vector<pair<int,pii>> EG;
int dp[1<<22][22];
 
int main()
{
        ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL);
        cin>>n>>ST>>EN;
        int ps = 0;
        for(int i=1; i<n; i++){
                int v,u,w; cin>>v>>u>>w;
                if(w!=0){
                        MP[v][u] = ps;
                        MP[u][v] = ps;
                        ps++;
                        EG.push_back({w,{v,u}});
                }
                eg[v].push_back({u,w});
                eg[u].push_back({v,w});
                g[v].push_back(u);
                g[u].push_back(v);
        }
        /**/
        pre_LCA();
        for(int i=1; i<=n; i++){
                p[i] = -1;
        }
        dfs(ST);
        for(int i=1; i<(1<<((int)EG.size()))+(1<<((int)EG.size())); i++){
                for(int j=0; j<((int)EG.size())+1; j++){
                        dp[i][j] = INF;
                }
        }
        for(ll i=1; i<(1<<((int)EG.size())); i++){
                int pos = i;
                while(pos>0){
                        int j = __builtin_ctz(pos);
                        pos -= (1<<j);
                        int x = i^(1<<j);
                        int V=EG[j].S.F , U=EG[j].S.S , W=EG[j].F;
                        if(req[W]!=(req[W]&x))continue;
                        if(req[V]!=(req[V]&x) && req[U]!=(req[U]&x))continue;
                        if(x==0){
                                dp[i][j] = DIS(ST,W) + min(DIS(W,V),DIS(W,U));
                                continue;
                        }
                        int POS=i;
                        while(POS>0){
                                int f = __builtin_ctz(POS);
                                POS -= 1<<f;
                                int v=EG[f].S.F , u=EG[f].S.S;
                                int D1=DIS(ST,v) , D2=DIS(ST,u);
                                if(D1>D2){
                                        swap(v,u);
                                }
                                dp[i][j] = min(dp[i][j] , dp[x][f]+DIS(v,W)+min(DIS(W,V),DIS(W,U)) );
                        }
                }
        }
        /***********************************/
        ps = ((int)EG.size());
        eg[EN].push_back({n+1,EN});
        eg[n+1].push_back({EN,EN});
        MP[EN][n+1] = ps;
        MP[EN][n+1] = ps;
        EG.push_back({EN,{EN,n+1}});
 
        for(ll i=(1<<ps); i<(1<<(ps+1)); i++){
                int j = ps;
                int x = i^(1<<j);
                int V=EG[j].S.F , U=EG[j].S.S , W=EG[j].F;
                if(req[W]!=(req[W]&x))continue;
                if(req[V]!=(req[V]&x) && req[U]!=(req[U]&x))continue;
                if(x==0){
                        dp[i][j] = DIS(ST,W) + min(DIS(W,V),DIS(W,U));
                        continue;
                }
                int POS=i;
                while(POS>0){
                        int f = __builtin_ctz(POS);
                        POS -= 1<<f;
                        int v=EG[f].S.F , u=EG[f].S.S;
                        int D1=DIS(ST,v) , D2=DIS(ST,u);
                        if(D1>D2){
                                swap(v,u);
                        }
                        dp[i][j] = min(dp[i][j] , dp[x][f]+DIS(v,W)+min(DIS(W,V),DIS(W,U)) );
                }
        }
        int ans = INF;
        for(int i=(1<<ps); i<(1<<(ps+1)); i++){
                ans = min(ans , dp[i][ps]);
        }
        /*ll ans = INF;
        for(int i=1; i<(1<<((int)EG.size())); i++)
        {
                for(int j=0; j<((int)EG.size()); j++){
                        int V=EG[j].S.F , U=EG[j].S.S;
                        if(DIS(V,ST)>DIS(U,ST)){
                                swap(V,U);
                        }
                        if(req[EN]!=(req[EN]&i))continue;
                        ans = min(ans , (ll)dp[i][j] + DIS(V,EN));
                }
        }*/
        if(ans==INF){
                cout<<-1;
                return 0;
        }
        cout<<ans;
        return 0;
}
/*
3
1 3
1 2 3
1 3 2
*/
/*
10
1 10
1 2 0
2 3 0
3 4 0
4 5 2
2 6 4
2 7 0
7 8 5
8 9 6
9 10 0
ans = 19
*/
/**
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: 23 / 23
• Subtask 2: 0 / 36
• Subtask 3: 0 / 41