[leetcode]133. Clone Graph@Java解题报告

https://leetcode.com/problems/clone-graph/description/

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 #.

1. First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
2. Second node is labeled as 1. Connect node 1 to node 2.
3. Third node is labeled as 2. Connect node 2 to node 2 (itself), thus forming a self-cycle.

Visually, the graph looks like the following:

       1      / \     /   \    0 --- 2         / \         \_/

package go.jacob.day815;import java.util.ArrayList;import java.util.HashMap;import java.util.Map;import java.util.Stack;/** * 133. Clone Graph * @author Jacob * 牛客的测试不够严谨，直接返回node也是可以通过的 *  * 以下分享DFS循环和递归实现 */public class Demo1 {/* * 循环实现 */public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {if (node == null)return null;// map存储旧节点到新节点的映射Map<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();UndirectedGraphNode head = new UndirectedGraphNode(node.label);map.put(node, head);// DFS需要用到栈Stack<UndirectedGraphNode> stack = new Stack<UndirectedGraphNode>();stack.push(node);while (!stack.isEmpty()) {UndirectedGraphNode root = stack.pop();ArrayList<UndirectedGraphNode> lists = new ArrayList<UndirectedGraphNode>();for (UndirectedGraphNode n : root.neighbors) {if (map.containsKey(n)) {lists.add(map.get(n));} else {UndirectedGraphNode n1 = new UndirectedGraphNode(n.label);stack.push(n);map.put(n, n1);lists.add(n1);}}System.out.println(map.containsKey(root));map.get(root).neighbors = lists;}return head;}/* * 递归实现 */private HashMap<Integer, UndirectedGraphNode> map = new HashMap<>();    public UndirectedGraphNode cloneGraph_1(UndirectedGraphNode node) {        return clone(node);    }    private UndirectedGraphNode clone(UndirectedGraphNode node) {        if (node == null) return null;                if (map.containsKey(node.label)) {            return map.get(node.label);        }        UndirectedGraphNode clone = new UndirectedGraphNode(node.label);        map.put(clone.label, clone);        for (UndirectedGraphNode neighbor : node.neighbors) {            clone.neighbors.add(clone(neighbor));        }        return clone;    }}