#include<iostream>
#include<queue>
#include<vector>
using namespace std;
int n, m, ans = 0, check[1001];
int main(void){
cin >> n >> m;
vector<vector<int> > g(n + 1);
int a, b;
for (int i = 0; i < m; i++){
cin >> a >> b;
g[a].push_back(b);
g[b].push_back(a);
}
queue<int> q;
for (int i = 1; i < n + 1; i++){
if (!check[i]){
ans++;
q.push(i);
check[i] = true;
while (!q.empty())
{
int now = q.front();
q.pop();
for (int j = 0; j < g[now].size(); j++){
if (!check[g[now][j]]){
q.push(g[now][j]);
check[g[now][j]] = true;
}
}
}
}
}
cout << ans << "\n";
return 0;
}
소스코드 : dfs
#include<iostream>
#include<vector>
using namespace std;
int n, m, ans, check[1001];
vector<vector<int> > g;
void dfs(int now){
check[now] = true;
for (int i = 0; i < g[now].size(); i++){
if (!check[g[now][i]])
dfs(g[now][i]);
}
}
int main(void){
cin >> n >> m;
g.resize(n + 1);
int a, b;
for (int i = 0; i < m; i++){
cin >> a >> b;
g[a].push_back(b);
g[b].push_back(a);
}
for (int i = 1; i < n + 1; i++){
if (!check[i]){
ans++;
dfs(i);
}
}
cout << ans << "\n";
return 0;
}
[출처 : BOJ, 문제에 대한 모든 권리는 BOJ(acmicpc.net, startlink)에 있음]