11724 연결 요소의 개수

https://www.acmicpc.net/problem/11724

#include <cstdio>
#include <vector>
using namespace std;
 
int n,m,u,v,c[1001],ans;
vector<int> a[1001];
 
void dfs(int x)
{
    c[x]=1;
    for(auto i : a[x])
        if(!c[i]) dfs(i);
}
 
int main()
{
    scanf("%d %d",&n,&m);
    while(m--)
    {
        scanf("%d %d",&u,&v);
        a[u].push_back(v);
        a[v].push_back(u);
    }
    for(int i=1;i<=n;i++)
        if(!c[i]) dfs(i),ans++;
    printf("%d\n",ans);
    return 0;
}