lintcode 容易题：Find the Connected Component in the Undirected Graph 找出无向图汇总的相连要素

题目：

找出无向图汇总的相连要素

请找出无向图中相连要素的个数。

图中的每个节点包含其邻居的 1 个标签和 1 个列表。（一个无向图的相连节点（或节点）是一个子图，其中任意两个顶点通过路径相连，且不与超级图中的其它顶点相连。）

样例

给定图:

A------B  C
\     |  |
\    |  |
\   |  |
\  |  |
D   E

返回

{A,B,D}, {C,E}

。其中有 2 个相连的元素，即

{A,B,D}, {C,E}

解题：

广度优先+递归，写不出来，程序来源

Java程序：

/**
* Definition for Undirected graph.
* class UndirectedGraphNode {
*     int label;
*     ArrayList<UndirectedGraphNode> neighbors;
*     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
* };
*/
public class Solution {
/**
* @param nodes a array of Undirected graph node
* @return a connected set of a Undirected graph
*/
public List<List<Integer>> connectedSet(ArrayList<UndirectedGraphNode> nodes) {
// Write your code here

int m = nodes.size();
Map<UndirectedGraphNode, Boolean> visited = new HashMap<>();

for (UndirectedGraphNode node : nodes){
visited.put(node, false);
}

List<List<Integer>> result = new ArrayList<>();

for (UndirectedGraphNode node : nodes){
if (visited.get(node) == false){
bfs(node, visited, result);
}
}

return result;
}

public void bfs(UndirectedGraphNode node, Map<UndirectedGraphNode, Boolean> visited, List<List<Integer>> result){

List<Integer>row = new ArrayList<>();

Queue<UndirectedGraphNode> queue = new LinkedList<>();
visited.put(node, true);
queue.offer(node);

while (!queue.isEmpty()){
UndirectedGraphNode u = queue.poll();
row.add(u.label);

for (UndirectedGraphNode v : u.neighbors){
if (visited.get(v) == false){
visited.put(v, true);
queue.offer(v);
}
}
}

Collections.sort(row);
result.add(row);

}
}

View Code
总耗时: 7732 ms

Python程序：