Archived | 310-01-ACOJ-0488-统计节点

#include <iostream>

using namespace std;

const int maxn = 100005;
int n, m, k;
int t_point[maxn], head[maxn], dist_1[maxn], dist_2[maxn], dist_3[maxn];
bool isImPoint[maxn];

struct edge {
    int to, next;
} g[maxn << 1];

int ecnt = 2;

void add_edge(int u, int v) {
    g[ecnt] = (edge) {v, head[u]};
    head[u] = ecnt ++;
}

void dfs(int u, int fa, int P) {
    for (int e = head[u]; e != 0; e = g[e].next) {
        int v = g[e].to;
        if (v == fa) continue;
        if (P == 1) dist_1[v] = dist_1[u] + 1;
        if (P == 2) dist_2[v] = dist_2[u] + 1;
        if (P == 3) dist_3[v] = dist_3[u] + 1;
        dfs(v, u, P);
    }
}

int main() {
        cin >> n >> m >> k;
    for (int i = 1; i <= m; i ++) {
        cin >> t_point[i];
        isImPoint[t_point[i]] = true;
    }
    for (int i = 1; i < n; i ++) {
        int u, v; cin >> u >> v;
        add_edge(u, v); add_edge(v, u);
    }
        dfs(1, 0, 1);
        int node_first = 0;
        for (int i = 1; i <= m; i ++)
                if (dist_1[t_point[i]] >= dist_1[node_first]) node_first = t_point[i];
        dfs(node_first, 0, 2);
        int node_second = 0;
        for (int i = 1; i <= m; i ++)
                if (dist_2[t_point[i]] >= dist_2[node_second]) node_second = t_point[i];
        dfs(node_second, 0, 3);
        int cnt = 0;
        for (int i = 1; i <= n; i ++) {
                if (isImPoint[i]) continue;
                if (dist_2[i] <= k && dist_3[i] <= k)
                        cnt ++;
        }
        cout << cnt << endl;
        return 0;
}