Submission #1307056

#	Time	Username	Problem	Language	Result	Execution time	Memory
1307056		saken03	Valley (BOI19_valley)	C++20	0 / 100	3096 ms	34052 KiB

valley

#include <iostream>
#include <map>
#include <vector>

#define pb push_back

#define fi first
#define se second

typedef long long ll;

using namespace std;

const int N = 1e5 + 5;
const ll INF = 1e18; 

int n, s, q, e;
pair<int, int> edge[N];
vector<int> g[N];

map<int, bool> shop;
map<pair<int, int>, ll> cost;

bool is_esc[N];

int in[N], out[N], clk, par[N];
ll dist[N];

void dfs(int v, int p = -1) {
    in[v] = ++clk; 
    par[v] = p;

    for (int to : g[v]) {
        if (to != p) {
            dist[to] = dist[v] + max(cost[{v, to}], cost[{to, v}]);
            dfs(to, v);
        }    
    }

    out[v] = ++clk;
}

bool subtree_of(int a, int b) {
    if (in[a] <= in[b] && out[b] <= out[a]) return 1;
    return 0;
}

ll magic[N];

void buildMagic(int v) {
    for (int to : g[v]) {
        if (to == par[v]) continue;
        buildMagic(to);
    }

    if (shop[v] == 1) {
        magic[v] = dist[v];
    }
    else 
        magic[v] = INF;

    for (int to : g[v]) {
        if (to == par[v]) continue;
        magic[v] = min(magic[v], magic[to]);
    }
}

void solve() {
    cin >> n >> s >> q >> e;

    for (int i = 1; i < n; i++) {
        int a, b, c;
        cin >> a >> b >> c;

        cost[{a, b}] = c;
        g[a].pb(b);
        g[b].pb(a);
        edge[i] = {a, b};
    }

    while (s--) {
        int c;
        cin >> c;
        shop[c] = 1;
    }

    dfs(e);
    buildMagic(e);

    for (int i = 1; i <= n; i++) {
        magic[i] -= 2 * 1ll * dist[i];
    }

    while (q--) {
        int i, r;
        cin >> i >> r;

        int a, b;
        a = edge[i].fi;
        b = edge[i].se;

        if (par[a] == b) swap(a, b); // a -> b (in tree)

        //cout << "a is " << a << ", b is " << b << '\n';

        if (subtree_of(e, r) && !subtree_of(b, r)) {
            cout << "escaped\n";
            continue;
        }

        int R = r;
        ll ans = INF;
    
        while (R != a) {
            ans = min(ans, magic[R]);
            R = par[R];
        }

        if (ans < 1e17) cout << dist[r] + ans << '\n';
        else cout << "00\n";
    }
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    solve();

    return 0;
}

• Subtask 1: 0 / 9
• Subtask 2: 0 / 27
• Subtask 3: 0 / 23
• Subtask 4: 0 / 41