Submission #687545

#	Time	Username	Problem	Language	Result	Execution time	Memory
687545		stanislavpolyn	Valley (BOI19_valley)	C++17	100 / 100	151 ms	23796 KiB

valley

#include <bits/stdc++.h>

#define fr(i, a, b) for (int i = (a); i <= (b); ++i)
#define rf(i, a, b) for (int i = (a); i >= (b); --i)
#define fe(x, y) for (auto& x : y)

#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define mt make_tuple

#define all(x) (x).begin(), (x).end()
#define pw(x) (1LL << (x))
#define sz(x) (int)(x).size()

using namespace std;

mt19937_64 rng(228);

#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template <typename T>
using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define fbo find_by_order
#define ook order_of_key

template <typename T>
bool umn(T& a, T b) {
    return a > b ? a = b, 1 : 0;
}
template <typename T>
bool umx(T& a, T b) {
    return a < b ? a = b, 1 : 0;
}

using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
template <typename T>
using ve = vector<T>;

const int N = 1e5 + 5;

int n, s, q, root;
ve<pii> g[N];
int w[N];
int p[N], pe[N];
int tin[N], tout[N], timer;
int who[N];
ll dep[N];
bool mark[N];
ll dp[N];
int sz[N];
int d[N];

void dfs(int v = root, int p = 0) {
    ::p[v] = p;
    tin[v] = timer++;

    if (mark[v]) {
        dp[v] = 0;
    } else {
        dp[v] = 1e18;
    }

    sz[v] = 1;

    fe (to, g[v]) {
        if (to.fi == p) continue;
        dep[to.fi] = w[to.se] + dep[v];
        who[to.se] = to.fi;
        pe[to.fi] = to.se;
        d[to.fi] = d[v] + 1;

        dfs(to.fi, v);

        sz[v] += sz[to.fi];
        umn(dp[v], dp[to.fi] + w[to.se]);
    }
    tout[v] = timer;
}

bool isUpper(int a, int b) {
    return tin[a] <= tin[b] && tout[a] >= tout[b];
}

int top[N];
int pos[N];
ve<int> st;

void hld(int v = root, int p = 0) {
    st.pb(v);
    pos[v] = sz(st) - 1;
    fe (to, g[v]) {
        if (to.fi == p) continue;

        if (g[v][0].fi == p || sz[to.fi] > sz[g[v][0].fi]) {
            swap(to, g[v][0]);
        }
    }
//    assert(g[v][0].fi != p);
    fe (to, g[v]) {
        if (to.fi == p) continue;

        if (to.fi == g[v][0].fi) {
            top[to.fi] = top[v];
            hld(to.fi, v);
        } else {
            top[to.fi] = to.fi;
            hld(to.fi, v);
        }
    }
}

ll add[N];

ll t[4 * N];

void build(int v = 1, int tl = 0, int tr = sz(st) - 1) {
    if (tl == tr) {
        t[v] = add[st[tl]] + dp[st[tl]];
        return;
    }
    int tm = (tl + tr) >> 1;
    build(v << 1, tl, tm);
    build(v << 1 | 1, tm + 1, tr);
    t[v] = min(t[v << 1], t[v << 1 | 1]);
}

ll get(int v, int tl, int tr, int l, int r) {
    if (l > r) {
        return 2e18;
    }
    if (tl == l && tr == r) {
        return t[v];
    }
    int tm = (tl + tr) >> 1;
    return min(get(v << 1, tl, tm, l, min(r, tm)),
               get(v << 1 | 1, tm + 1, tr, max(tm + 1, l), r));
}

ll get(int l, int r) {
    return get(1, 0, sz(st) - 1, l, r);
}

int main() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#else
    ios::sync_with_stdio(0);
    cin.tie(0);
#endif

    cin >> n >> s >> q >> root;

    fr (i, 1, n - 1) {
        int a, b;
        cin >> a >> b >> w[i];

        g[a].pb({b, i});
        g[b].pb({a, i});
    }

    fr (i, 1, s) {
        int x;
        cin >> x;
        mark[x] = 1;
    }

    dfs();
    top[root] = root;
    hld();

    {
        rf (i, sz(st) - 2, 0) {
            if (top[st[i + 1]] == top[st[i]]) {
                assert(p[st[i + 1]] == st[i]);
                add[st[i]] = add[st[i + 1]] + w[pe[st[i + 1]]];
            }
        }
    }

    build();

    fr (i, 1, q) {
        int idx, v;
        cin >> idx >> v;

        int u = who[idx];

        if (!isUpper(u, v)) {
            cout << "escaped\n";
        } else {
            if (mark[v]) {
                cout << "0\n";
                continue;
            }

            // faster
            {
                int cur = v;
                ll best = 1e18;
                ll len = 0;

                int jump = 0;
                while (1) {
                    if (isUpper(top[cur], u)) {
                        assert(top[cur] == top[cur]);
                        ll mn = get(pos[u], pos[cur]);
                        mn -= add[cur];
                        umn(best, mn + len);

                        break;
                    }
                    ll mn = get(pos[top[cur]], pos[cur]);
                    mn -= add[cur];
                    umn(best, mn + len);

                    len += add[top[cur]] - add[cur];
                    len += w[pe[top[cur]]];
                    cur = p[top[cur]];
                    jump++;
//                    cout << cur << " " << top[cur] << " " << p[top[cur]] << "\n";
                }
                assert(jump <= 20);

                if (best == 1e18) {
                    cout << "oo\n";
                } else {
                    cout << best << "\n";
                }
            }
//
//            int cur = v;
//            ll best = 1e18;
//            ll len = 0;
//            while (1) {
//                umn(best, len + dp[cur]);
//                if (cur == u) {
//                    break;
//                }
//                len += w[pe[cur]];
//                cur = p[cur];
//            }
//
//            if (best == 1e18) {
//                cout << "oo\n";
//            } else {
//                cout << best << "\n";
//            }
        }
    }

    return 0;
}

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 41 / 41