HDU - 1213 dfs求联通块or并查集

思路：给定一个无向图，判断有几个联通块。

AC代码

#include <cstdio>
#include <cmath>
#include <algorithm>
#include <cstring>
#include <utility>
#include <string>
#include <iostream>
#include <map>
#include <set>
#include <vector>
#include <queue>
#include <stack>
using namespace std;
#pragma comment(linker, "/STACK:1024000000,1024000000")
#define eps 1e-10
#define inf 0x3f3f3f3f
#define PI pair<int, int>
typedef long long LL;
const int maxn = 1000 + 5;
vector<int>G[maxn];
int vis[maxn];
void dfs(int u) {
	vis[u] = 1;
	int n = G[u].size();
	for(int i = 0; i < n; ++i) {
		int v = G[u][i];
		if(vis[v] && v != u)  continue;
		dfs(v);
	}
}
int main() {
	int T, n, m;
	scanf("%d", &T);
	while(T--) {
		scanf("%d%d", &n, &m);
		for(int i = 1; i <= n; ++i) G[i].clear();
		int x, y;
		for(int i = 0; i < m; ++i) {
			scanf("%d%d", &x, &y);
			G[x].push_back(y);
			G[y].push_back(x);
		}
		memset(vis, 0, sizeof(vis));
		int ans = 0;
		for(int i = 1; i <= n; ++i) {
			if(!vis[i]) {
				dfs(i);
				++ans;
			}
		}
		printf("%d\n", ans);
	}
	return 0;
}

如有不当之处欢迎指出！