【題解】ZeroJudge c812: 1. 觀光景點

#include <iostream>
#include <cstring>
#include <map>
#include <string>
#include <algorithm>
#include <set>
#include <vector>
using namespace std;

map <int, vector<pair<int, int> > > mp;
int num;
int start;
int q;
int arr[5005];

void func(int n, int last, int mini){
    for (pair<int, int> p: mp[n]){
        if (p.first == last){
            continue;
        }else{
            arr[p.first] = min(p.second, mini);
            func(p.first, n, min(p.second, mini));
        }
    }
}

int main(){
    while (cin >> num >> start >> q){
        mp.clear();
        int a, b, c, ans = 0, maxi = 0;
        for (int i = 0; i < num-1; i++){
            cin >> a >> b >> c;
            if (c > maxi) maxi = c;
            mp[a].push_back({b, c});
            mp[b].push_back({a, c});
        }
        func(start, num+1, maxi);
        for (int i = 1; i <= num; i++){
            if (i == start) continue;
            if (arr[i] >= q) ans++;
        }
        cout << ans << "\n";
    }
}

import sys
sys.setrecursionlimit(100000)

def dfs(now, pre, mn):
    global ans
    ans += 1
    for (nxt, w) in g[now]:
        if nxt != pre and w >= q:
            dfs(nxt, now, min(mn, w))


N, Vk, q = map(int, input().split())
g = {}
for _ in range(N-1):
    u, v, w = map(int, input().split())
    if u in g:
        g[u].append((v, w))
    else:
        g[u] = [(v, w)]

    if v in g:
        g[v].append((u, w))
    else:
        g[v] = [(u, w)]

ans = -1
dfs(Vk, Vk, 2e9)
print(ans)