Language: C++

#include <bits/stdc++.h>

using namespace std;
#define mygc(c) (c)=getchar_unlocked()
#define mypc(c) putchar_unlocked(c)
#define ll long long
#define ull unsigned ll
void reader(int *x) { int k, m = 0; *x = 0; for (;;) { mygc(k); if (k == '-') { m = 1; break; }if ('0' <= k&&k <= '9') { *x = k - '0'; break; } }for (;;) { mygc(k); if (k<'0' || k>'9')break; *x = (*x) * 10 + k - '0'; }if (m)(*x) = -(*x); }
void reader(ll *x) { int k, m = 0; *x = 0; for (;;) { mygc(k); if (k == '-') { m = 1; break; }if ('0' <= k&&k <= '9') { *x = k - '0'; break; } }for (;;) { mygc(k); if (k<'0' || k>'9')break; *x = (*x) * 10 + k - '0'; }if (m)(*x) = -(*x); }
void reader(double *x) { scanf("%lf", x); }
int reader(char c[]) { int i, s = 0; for (;;) { mygc(i); if (i != ' '&&i != '\n'&&i != '\r'&&i != '\t'&&i != EOF) break; }c[s++] = i; for (;;) { mygc(i); if (i == ' ' || i == '\n' || i == '\r' || i == '\t' || i == EOF) break; c[s++] = i; }c[s] = '\0'; return s; }
template <class T, class S> void reader(T *x, S *y) { reader(x); reader(y); }
template <class T, class S, class U> void reader(T *x, S *y, U *z) { reader(x); reader(y); reader(z); }
template <class T, class S, class U, class V> void reader(T *x, S *y, U *z, V *w) { reader(x); reader(y); reader(z); reader(w); }

void writer(int x, char c) { int s = 0, m = 0; char f[10]; if (x<0)m = 1, x = -x; while (x)f[s++] = x % 10, x /= 10; if (!s)f[s++] = 0; if (m)mypc('-'); while (s--)mypc(f[s] + '0'); mypc(c); }
void writer(ll x, char c) { int s = 0, m = 0; char f[20]; if (x<0)m = 1, x = -x; while (x)f[s++] = x % 10, x /= 10; if (!s)f[s++] = 0; if (m)mypc('-'); while (s--)mypc(f[s] + '0'); mypc(c); }
void writer(double x, char c) { printf("%.15f", x); mypc(c); }
void writer(const char c[]) { int i; for (i = 0; c[i] != '\0'; i++)mypc(c[i]); }
void writer(const char x[], char c) { int i; for (i = 0; x[i] != '\0'; i++)mypc(x[i]); mypc(c); }
template<class T> void writerLn(T x) { writer(x, '\n'); }
template<class T, class S> void writerLn(T x, S y) { writer(x, ' '); writer(y, '\n'); }
template<class T, class S, class U> void writerLn(T x, S y, U z) { writer(x, ' '); writer(y, ' '); writer(z, '\n'); }
template<class T> void writerArr(T x[], int n) { int i; if (!n) { mypc('\n'); return; }rep(i, n - 1)writer(x[i], ' '); writer(x[n - 1], '\n'); }

#define rep(i,n)for(int i=0;i<n;i++)
vector<int>E[100000];
int u[200000], v[200000], r[200000], ans[200000], d[100000]{ 1 }, cnt = 1;
char b[200000], ok[100000]{ 1 };
deque<int>que;

void bfs(int u, char t) {
	que.emplace_back(u);
	while (!que.empty()) {
		int p = que.front(); que.pop_front();
		for (int v : E[p]) {
			if (t) {
				if (d[v] > d[p] && !ok[v]) {
					ok[v] = 1; cnt++; que.emplace_back(v);
				}
			}
			else if (!d[v]) {
				d[v] = d[p] + 1; que.emplace_back(v);
			}
		}
	}
}
int main() {
	int n, m, q; reader(&n); reader(&m); reader(&q);
	rep(i, m) {
		reader(&u[i]); reader(&v[i]);
		u[i]--; v[i]--;
		E[u[i]].emplace_back(v[i]); E[v[i]].emplace_back(u[i]);
	}
	bfs(0, 0);
	rep(i, m) {
		if (d[u[i]] > d[v[i]])swap(u[i], v[i]);
	}
	rep(i, n)E[i].clear();
	rep(i, q) {
		reader(&r[i]); r[i]--;
		b[r[i]] = 1;
	}
	rep(i, m) {
		if (!b[i]) {
			if (d[v[i]] > d[u[i]]) {
				E[u[i]].emplace_back(v[i]);
			}
		}
	}
	bfs(0, 1);
	for (int i = q - 1; i >= 0; i--) {
		ans[i] = n - cnt;
		if (d[v[r[i]]] > d[u[r[i]]] && !ok[v[r[i]]]) {
			E[u[r[i]]].emplace_back(v[r[i]]);
			if (ok[u[r[i]]]) {
				cnt++; ok[v[r[i]]] = 1;
				bfs(v[r[i]], 1);
			}
		}
	}
	rep(i, q)writerLn(ans[i]);
}

Compiler output:
a.cc: In function 'void writerArr(T*, int)':
a.cc:24:88: error: there are no arguments to 'rep' that depend on a template parameter, so a declaration of 'rep' must be available [-fpermissive]
   24 | template<class T> void writerArr(T x[], int n) { int i; if (!n) { mypc('\n'); return; }rep(i, n - 1)writer(x[i], ' '); writer(x[n - 1], '\n'); }
      |                                                                                        ^~~
a.cc:24:88: note: (if you use '-fpermissive', G++ will accept your code, but allowing the use of an undeclared name is deprecated)
a.cc:24:101: error: expected ';' before 'writer'
   24 | template<class T> void writerArr(T x[], int n) { int i; if (!n) { mypc('\n'); return; }rep(i, n - 1)writer(x[i], ' '); writer(x[n - 1], '\n'); }
      |                                                                                                     ^~~~~~
      |                                                                                                     ;