[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 

#

.
First node is labeled as 

0

. Connect node 

0

 to
both nodes 

1

 and 

2

.
Second node is labeled as 

1

. Connect node 

1

 to
node 

2

.
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;
}

}