图的联通分量个数统计（判断图是否联通）

题目链接：https://pintia.cn/problem-sets/994805046380707840/problems/994805063963230208

基本上是裸的，直接看代码吧

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int inf=1<<30;
const double pi=acos(-1);
const int mod=998244353;
const int maxn=510;
const int maxm=6300;
int e[maxn][maxn];int n,m,cnt;
int vis[maxn];
void dfs(int x){
    vis[x]=1;
    for(int i=0;i<n;i++){
        if(!vis[i]&&e[x][i]){
            dfs(i);
        }
    }
}
int count(){
    int cnt=0;
    memset(vis,0,sizeof(vis));
    for(int i=0;i<n;i++){
        if(!vis[i]){
            cnt++;
            dfs(i);
        }
    }
    return cnt;
}
int main(){
    scanf("%d%d",&n,&m);
    int x,y;
    for(int i=0;i<m;i++){
        scanf("%d%d",&x,&y);
        e[x][y]=e[y][x]=1;    
    }
    cnt=count();
    int k;scanf("%d",&k);
    for(int i=0;i<k;i++){
        scanf("%d",&x);
        for(int i=0;i<n;i++){
            if(e[x][i]){
                e[x][i]=e[i][x]=0;
            }
        }
        int now=count();
        if(now-cnt>1){
            printf("Red Alert: City %d is lost!
",x);
        }else{
            printf("City %d is lost.
",x);
        }cnt=now;
        if(i==n-1) {
            printf("Game Over.
");break;
        }        
    }
    return 0;
}