有问题尚未解决

#include <iostream>
#include <vector>
#include <queue>
#include <cstring>
using namespace std;

const int N = 1e6+10;
const int M = 2e6+10;

int n, m, q;
int dist[N][2];
bool st[N][2];

struct node{
    int v, st;
};

vector<int> h[N];

void bfs(){
    queue<node> q;
    q.push({1, 0});
    dist[1][0] = 0;
    st[1][0] = 1;
    while(q.size()){
        auto [t, step] = q.front();
        q.pop();
        // if(st[t][step])continue; 不能加这句代码，原因未知
        st[t][step] = 1; //这句代码似乎不必要出现
        for(auto u:h[t]){
            if(st[u][!step]) continue;
            dist[u][!step] = dist[t][step] + 1;
            st[u][!step] = 1;
            q.push({u, !step});
        }
    }
}

int main(){
    memset(dist, 0x3f, sizeof dist);
    cin >> n >> m >> q;
    int a, b;
    for (int i = 1; i <= m; i ++ ){
        cin >> a >> b;
        h[a].push_back(b);
        h[b].push_back(a);
    }

    bfs();

    int A, L;
    for (int i = 1; i <= q; i ++ ){
        cin >> A >> L;
        if(h[1].empty()) cout << "No" << endl;
        else if(dist[A][L&1] <= L)cout << "Yes" << endl;
        else cout << "No" << endl;
    }
    return 0;
}