CF training season 2 episode 2 problem E(Accepted!)

#include <iostream>
#include <iomanip>
#include <stdio.h>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <cassert>

#define pb push_back
#define mp make_pair
#define forn(i, n) for(int i = 0; i < (int)(n); i++)
#define X first
#define Y second
#define sz(a) (int)((a).size())
#define all(a) (a).begin(), (a).end()

using namespace std;

typedef long long li;
typedef long double ld;
typedef pair<int, int> pt;

const int INF = (int)(1e9);
const li INF64 = (li)(INF) * (li)(INF);
const ld eps = 1e-9;
const ld pi = (ld)(3.1415926535897932384626433832795);

const int dx4[] = {-1, 0, 1, 0};
const int dy4[] = {0, 1, 0, -1};

const int ddx[] = {-1, 1, 1, -1};
const int ddy[] = {1, 1, -1, -1};

const int N = 1e5;

vector<pair<int, int> > g[N];
int n, m, A, k;
bool used[N];
int dist[N];

int main()
{
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    while(cin >> n >> m >> A >> k)
    {
        if(n + m + A + k == 0)
            break;

        for(int i = 0; i < N; i++)
            g[i].clear();

        memset(used, false, sizeof used);
        memset(dist, -1, sizeof dist);

        forn(i, m)
        {
            int a, b, w;
            scanf("%d %d %d", &a, &b, &w);
            g[a].pb(mp(b, w));
            g[b].pb(mp(a, w));
        }

        int sz = n;

        forn(kk, A)
        {
            int v;
            scanf("%d", &v);

            queue<int> q;
            q.push(v);
            if(!used[v])
            {
                used[v] = true;
                sz--;
            }

            dist[v] = 0;

            while(!q.empty())
            {
                int v = q.front();
                q.pop();

                forn(i, g[v].size())
                {
                    int to = g[v][i].X;
                    int cost = g[v][i].Y;
                    if(dist[v] + cost < k && (dist[v] + cost < dist[to] || dist[to] == -1))
                    {
                        dist[to] = dist[v] + cost;
                        q.push(to);
                        if(!used[to])
                        {
                            used[to] = true;
                            sz--;
                        }
                    }
                }
            }

            printf("%d ", sz);
        }

        printf("\n");
    }
    return 0;
}