Submission #999079

#	Time	Username	Problem	Language	Result	Execution time	Memory
999079		vjudge1	LOSTIKS (INOI20_lostiks)	C++17	0 / 100	53 ms	96860 KiB

Main

#include <bits/stdc++.h>
#define ll long long
#define endl "\n"

using namespace std;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
const ll N = 1e6 + 5, lg = 20;
vector<pair<ll, ll>> g[N];
ll need[N], comp[N], depth[N], up[lg][N];
ll vals[lg], dp[1 << lg][lg];
void dfs(ll v, ll par = 0)
{
    up[0][v] = par;
    for (ll i = 1; i < lg; i++)
        up[i][v] = up[i - 1][up[i - 1][v]];
    for (auto [to, w] : g[v])
        if (to != par)
        {
            if (w != 0)
                need[to] = need[v] | (1 << comp[w]);
            else need[to] = need[v];
            depth[to] = depth[v] + 1;
            dfs(to, v);
        }
}
ll lca(ll a, ll b)
{
    if (depth[a] < depth[b])
        swap(a, b);
    for (ll bit = lg - 1; bit >= 0; bit--)
        if (depth[a] - (1 << bit) >= depth[b])
            a = up[bit][a];
    if (a == b)
        return a;
    for (ll bit = lg - 1; bit >= 0; bit--)  if (up[bit][a] != up[bit][b]) a = up[bit][a], b = up[bit][b];
    return up[0][a];
}
ll dist(ll a, ll b)
{
    return depth[a] + depth[b] - depth[lca(a, b)] * 2;
}
void solve()
{
    ll n;
    cin >> n;
    ll s, t;
    cin >> s >> t;
    array<ll, 3> e[n - 1];
    for (ll i = 0; i < n - 1; i++)
    {
        cin >> e[i][0] >> e[i][1] >> e[i][2];
        g[e[i][0]].push_back(make_pair(e[i][1], e[i][2]));
        g[e[i][1]].push_back(make_pair(e[i][0], e[i][2]));
    }
        ll sz = 0;
    {
        set<ll> tmp;
        for (ll i = 1; i <= n; i++)
        for (auto [j, w] : g[i])
            if (w)
            tmp.insert(w);
        tmp.insert(s);
        tmp.insert(t);
        for (ll i : tmp) comp[i] = sz, vals[sz++] = i;
    }
    dfs(s, s);
    ll dp[1 << sz][sz];
    for (ll i = 0; i < (1 << sz); i++)
    for (ll j = 0; j < sz; j++)
        dp[i][j] = 1e18;
    dp[1 << comp[s]][comp[s]] = 0;
    for (ll msk = 0; msk < (1 << sz); msk++) if (msk != comp[s])
    {
        for (ll i = 0; i < sz; i++)
        if (msk >> i & 1 and ((msk ^ (1 << i)) & need[vals[i]]) == need[vals[i]])
        for (ll j = 0; j < sz; j++)
            if ((msk >> j & 1) and j != i)
                dp[msk][i] = min(dp[msk][i], dp[msk ^ (1 << i)][j] + dist(vals[i], vals[j]));
    }
    ll ans = 1e18;
    for (ll msk = 0; msk < (1 << sz); msk++)
        ans = min(ans, dp[msk][comp[t]]);
    if (ans == 1e18)
        ans = -1;
    cout << ans << endl;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    ll t = 1;
    // precomp();
    // cin >> t;
    for (ll cs = 1; cs <= t; cs++)
        solve();
    // cerr << "\nTime elapsed: " << clock() * 1000.0 / CLOCKS_PER_SEC << " ms\n";
}

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