C. Kefa and Park

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

class Tree {
  public:
    int n, m, ans;
    vector<vector<int>> adj;
    vector<int> has_cat;
    Tree(int n, int m) {
        this->n = n;
        this->m = m;
        ans = 0;
        adj.resize(n);
        has_cat.resize(n);
    }

    void dfs(int src, int par, int cons_cat_count, bool ok) {
        if (has_cat[src]) {
            cons_cat_count++;
        }
        if (cons_cat_count > m) {
            ok = false;
        }
        if (!has_cat[src]) {
            cons_cat_count = 0;
        }

        // Add contribution if it is a leaf vertex.
        // To identify a leaf vertex:
        // 1. It should not be root.
        // 2. It should have exactly one element in adjacency list.
        if (ok && par != -1 && adj[src].size() == 1) {
            ans++;
        }

        for (auto child : adj[src]) {
            if (child != par) {
                dfs(child, src, cons_cat_count, ok);
            }
        }
    }
};

void solve() {
    int n, m;
    cin >> n >> m;
    Tree t(n, m);

    for (int i = 0; i < n; i++) {
        cin >> t.has_cat[i];
    }

    auto &adj = t.adj;
    for (int i = 0; i < n - 1; i++) {
        int x, y;
        cin >> x >> y;
        x--;
        y--;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }

    t.dfs(0, -1, 0, true);
    cout << t.ans << endl;
}

int main() {
    solve();
    return 0;
}

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

class Tree {
  public:
    int n, m, ans;
    vector<vector<int>> adj;
    vector<int> has_cat;
    Tree(int n, int m) {
        this->n = n;
        this->m = m;
        ans = 0;
        adj.resize(n);
        has_cat.resize(n);
    }

    void dfs(int src, int par, int cons_cat_count) {
        cons_cat_count += has_cat[src];
        if (cons_cat_count > m) {
            return;
        }
        if (!has_cat[src]) {
            cons_cat_count = 0;
        }

        // Add contribution if it is a leaf vertex.
        // To identify a leaf vertex:
        // 1. It should not be root.
        // 2. It should have exactly one element in adjacency list.
        if (par != -1 && adj[src].size() == 1) {
            ans++;
        }

        for (auto child : adj[src]) {
            if (child != par) {
                dfs(child, src, cons_cat_count);
            }
        }
    }
};

void solve() {
    int n, m;
    cin >> n >> m;
    Tree t(n, m);

    for (int i = 0; i < n; i++) {
        cin >> t.has_cat[i];
    }

    auto &adj = t.adj;
    for (int i = 0; i < n - 1; i++) {
        int x, y;
        cin >> x >> y;
        x--;
        y--;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }

    t.dfs(0, -1, 0);
    cout << t.ans << endl;
}

int main() {
    solve();
    return 0;
}