Submission #526259

#	Time	Username	Problem	Language	Result	Execution time	Memory
526259		Evang	Valley (BOI19_valley)	C++17	100 / 100	255 ms	40820 KiB

valley

#include <bits/extc++.h>
using namespace std;
using namespace __gnu_pbds;

#ifdef _DEBUG
#define dout(x) clog << "Line " << __LINE__ << ": " << #x << "=" << (x) << el
#else
#define dout(x)
#endif

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define uid(a,b) uniform_int_distribution<int>(a,b)(rng)

#define ins insert
#define ssize(x) (int((x).size()))
#define bs(args...) binary_search(args)
#define lb(args...) lower_bound(args)
#define ub(args...) upper_bound(args)
#define all(x) (x).begin(),(x).end()
#define mp(a, b) make_pair(a, b)
#define mt(args...) make_tuple(args)
#define pb(x) push_back(x)
#define eb(args...) emplace_back(args)
#define ff first
#define ss second
#define die exit(0)

template<typename T>
using vc = vector<T>;
template<typename T>
using uset = unordered_set<T>;
template<typename A, typename B>
using umap = unordered_map<A, B>;
template<typename T, typename Comp>
using pq = std::priority_queue<T, vc<T>, Comp>;
template<typename T>
using maxpq = pq<T, less<T>>;
template<typename T>
using minpq = pq<T, greater<T>>;
template<typename T>
using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

using db = double;
using ld = long double;
using ll = long long;
using ull = unsigned long long;
using pi = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vc<int>;
using vll = vc<ll>;
using vpi = vc<pi>;
using vpll = vc<pll>;
using str = string;

constexpr char el = '\n';
constexpr char sp = ' ';
constexpr int inf = 0x3f3f3f3f;
constexpr ll llinf = 0x3f3f3f3f3f3f3f3fLL;
// ---------------------------------------------------------------------


const int LG = 20;
const int N = 1e5+5;
int n, s, q, e, up[LG][N], dep[N];
ll mag[LG][N], dis[N];
tuple<int, int, int> eg[N];
bool is_shop[N];
vpi adj[N];

int anc(int x, int k){
    for(int i = 0; k > 0; ++i){
        if(k&1)
            x = up[i][x];
        k /= 2;
    }
    return x;
}

int lca(int a, int b){
    a = anc(a, max(0, dep[a]-dep[b]));
    b = anc(b, max(0, dep[b]-dep[a]));
    if(a==b)
        return a;

    for(int i = LG-1; i >= 0; --i)
        if(up[i][a]!=up[i][b]){
            a = up[i][a];
            b = up[i][b];
        }

    return up[0][a];
}

void dfs(int v, int p){
    up[0][v] = p;
    if(is_shop[v])
        mag[0][v] = dis[v];
    else
        mag[0][v] = llinf;

    for(auto[u, w]: adj[v]){
        if(u==p)
            continue;
        dep[u] = dep[v] + 1;
        dis[u] = dis[v] + w;
        dfs(u, v);
        mag[0][v] = min(mag[0][v], mag[0][u]);
    }
}

signed main() {
    ios::sync_with_stdio(0); cin.tie(0);
    cout << fixed; clog << fixed; clog << unitbuf;
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    freopen("debug.txt", "w", stderr);
#else
    //freopen(".in", "r", stdin);
    //freopen(".out", "w", stdout);
#endif

    cin >> n >> s >> q >> e;
    for(int i = 1; i < n; ++i){
        int a, b, w;
        cin >> a >> b >> w;
        adj[a].eb(b, w);
        adj[b].eb(a, w);
        eg[i] = {a, b, w};
    }

    while(s--){
        int x;
        cin >> x;
        is_shop[x] = 1;
    }

    dfs(e, 0);
    for(int i = 1; i <= n; ++i)
        if(mag[0][i]<llinf)
            mag[0][i] -= 2*dis[i];

#ifdef _DEBUG
    clog << "Line " << __LINE__ << ":\n";
    for(int i = 1; i <= n; ++i)
        clog << dep[i] << sp << dis[i] << el;
    clog << el;
#endif

    for(int i = 1; i < LG; ++i)
        for(int j = 1; j <= n; ++j){
            up[i][j] = up[i-1][up[i-1][j]];
            mag[i][j] = min(mag[i-1][j], mag[i-1][up[i-1][j]]);
        }

    while(q--){
        int i, r;
        cin >> i >> r;
        auto[v, u, _] = eg[i];
        if(lca(v, r)!=v || lca(u, r) != u){
            cout << "escaped\n";
            continue;
        }
        if(dep[v]<dep[u])
            swap(v, u);
        u = r;

        ll mi = llinf;
        for(int i = LG-1; i >= 0; --i)
            if(dep[up[i][r]] >= dep[v]){
                mi = min(mi, mag[i][r]);
                r = up[i][r];
            }
        mi = min(mi, mag[0][r]);

        if(mi >= llinf)
            cout << "oo\n";
        else
            cout << dis[u] + mi << el;
    }
}

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