玄关，这道题真的用不了最短路吗？

/*
Luogu P6111 MooTube S
https://www.luogu.com.cn/problem/P6111
*/
#include "iostream"
#include "cstring"
#include "queue"
#define pii pair<int,int>
using namespace std;
int n, Q, head[5005], idx, k, v, temp1, temp2, temp3, ans1, ans2;
int dis[5005];
bool book[5005], flag[5005];
struct edge{
	int to, nxt, w;
}e[100005];
void add_edge(int u, int v_, int w){
	e[++idx].to=v_;
	e[idx].w=w;
	e[idx].nxt=head[u];
	head[u]=idx;
}
class cmp{
public:
    bool operator() (pii a,pii b){
        return b.second >= a.second;
    }
};
void dijkstra(int st){
    memset(dis, 0x3f, sizeof(dis)), memset(flag, 0, sizeof(flag));
    ans1=0, flag[st]=true;
    priority_queue<pii, vector<pii>, cmp>q;
    q.push(make_pair(st, dis[st]));
    while(!q.empty()){
        int temp=q.top().first, to;
        book[temp]=false;
        q.pop();
        for(int i=head[temp];i;i=e[i].nxt){
            to=e[i].to;
            if(min(dis[temp], e[i].w) < dis[to]){
                dis[to]=min(dis[temp], e[i].w);
                if(dis[to]>=k && !flag[to]) ans1++; flag[to]=true;
                if(!book[to]){
                    book[to]=true;
                    q.push(make_pair(to, dis[to]));
                }
            }
        }
    }
}
int main(){
	scanf("%d%d", &n, &Q);
	for(int i=1;i<n;i++){
		scanf("%d%d%d", &temp1, &temp2, &temp3);
		add_edge(temp1, temp2, temp3);
		add_edge(temp2, temp1, temp3);
	}
	while(Q--){
		scanf("%d%d", &k, &v);
        dijkstra(v);
		printf("%d\n", ans1);
	}
}