DFS遍历图即可，某个城市失去将vis置为true即可，注意每次都要vis重新初始化
#include<iostream>
#include<cstring>
using namespace std;
const int maxv = 1e3 + 10;
int G[maxv][maxv];
bool vis[maxv];
int n, m, k;
void DFS(int v)
{
vis[v] = true;
for (int i = 1; i <= n; i++)
{
if (!vis[i] && G[v][i])DFS(i);
}
}
int main()
{
scanf("%d%d%d", &n, &m, &k);
for (int i = 0; i < m; i++)
{
int x, y;
scanf("%d%d", &x, &y);
G[x][y] = G[y][x] = 1;
}
while (k--)
{
int query;
scanf("%d", &query);
memset(vis, false, sizeof(vis));
vis[query] = true;
int ans = 0;
for (int i = 1; i <= n; i++)
{
if (!vis[i])
{
DFS(i);
ans++;
}
}
printf("%d\n", ans - 1);
}
return 0;
}
