使用深度优先搜索（DFS）将所有连接的单个组件标记为已访问：

dfs(node u)
  for each node v connected to u :
    if v is not visited :
      visited[v] = true
      dfs(v)


for each node u:
  if u is not visited :
    visited[u] = true
    connected_component += 1
    dfs(u)

最好的方法是使用线性时间O（n）的简单方法。
由于您询问了联合查找算法：

for each node parent[node] = node

for each node u :
   for each node v connected to u :  
       if findset(u)!=findset(v) :
           union(u,v)

**I assume you know about how findset and union works **  
for each node if (parent[node] == node)  
    connected_component += 1