題目:
Clone an undirected graph. Each node in the graph contains a label
and
a list of its neighbors
.
OJ's undirected graph serialization:
Nodes are labeled uniquely.
We use#
as a separator for each node, and ,
as
a separator for node label and each neighbor of the node.
As an example, consider the serialized graph {0,1,2#1,2#2,2}
.
The graph has a total of three nodes, and therefore contains three parts as separated by #
.
- First node is labeled as
0
. Connect node0
to both nodes1
and2
. - Second node is labeled as
1
. Connect node1
to node2
. - Third node is labeled as
2
. Connect node2
to node2
(itself), thus forming a self-cycle.
Visually, the graph looks like the following:
1 / \ / \ 0 --- 2 / \ \_/
代碼:
- /**
- * Definition for undirected graph.
- * class UndirectedGraphNode {
- * int label;
- * ArrayList<UndirectedGraphNode> neighbors;
- * UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
- * };
- */
- public class Solution {
- Map<Integer, UndirectedGraphNode> nodeMap = new HashMap<Integer, UndirectedGraphNode>();
- public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
- // Note: The Solution object is instantiated only once and is reused by each test case.
- if (node == null) {
- return null;
- }
- LinkedList<UndirectedGraphNode> stack = new LinkedList<UndirectedGraphNode>();
- //Map<Integer, UndirectedGraphNode> nodeMap = new HashMap<Integer, UndirectedGraphNode>();
- nodeMap.clear();
- Set<Integer> isFound = new HashSet<Integer>();
- stack.addLast(node);
- UndirectedGraphNode head = null;
- while (!stack.isEmpty()) {
- UndirectedGraphNode first = stack.getFirst();
- stack.removeFirst();
- int label = first.label;
- UndirectedGraphNode n = nodeMap.get(label);
- if (n == null) {
- n = new UndirectedGraphNode(label);
- nodeMap.put(label, n);
- }
- if (head == null) {
- head = n;
- }
- if (!isFound.contains(label)) {
- isFound.add(label);
- ArrayList<UndirectedGraphNode> neighbors = first.neighbors;
- for (UndirectedGraphNode nb : neighbors) {
- UndirectedGraphNode nn = nodeMap.get(nb.label);
- if (nn == null) {
- nn = new UndirectedGraphNode(nb.label);
- nodeMap.put(nb.label, nn);
- stack.addLast(nb);
- }
- n.neighbors.add(nn); }
- }
- }
- return head;
- }
- }