Given a reference of a node in a connected undirected graph.
Return a deep copy (clone) of the graph.
Each node in the graph contains a value (int) and a list (List[Node]) of its neighbors.
class Node {
public int val;
public List<Node> neighbors;
}
Test case format:
For simplicity, each node’s value is the same as the node’s index (1-indexed). For example, the first node with val == 1, the second node with val == 2, and so on. The graph is represented in the test case using an adjacency list.
An adjacency list is a collection of unordered lists used to represent a finite graph. Each list describes the set of neighbors of a node in the graph.
The given node will always be the first node with val = 1. You must return the copy of the given node as a reference to the cloned graph.
Example 1:
Input: adjList = [[2,4],[1,3],[2,4],[1,3]]
Output: [[2,4],[1,3],[2,4],[1,3]]
Explanation: There are 4 nodes in the graph.
1st node (val = 1)'s neighbors are 2nd node (val = 2) and 4th node (val = 4).
2nd node (val = 2)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).
3rd node (val = 3)'s neighbors are 2nd node (val = 2) and 4th node (val = 4).
4th node (val = 4)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).
Example 2:
Input: adjList = [[]]
Output: [[]]
Explanation: Note that the input contains one empty list. The graph consists of only one node with val = 1 and it does not have any neighbors.
Example 3:
Input: adjList = []
Output: []
Explanation: This an empty graph, it does not have any nodes.
Constraints:
"""
# Definition for a Node.
class Node:
def __init__(self, val = 0, neighbors = None):
self.val = val
self.neighbors = neighbors if neighbors is not None else []
"""
class Solution:
def cloneGraph(self, root: 'Node') -> 'Node':
# corner case
if root is None:
return None
# clone nodes by BFS
old2new = dict() # key: old node, val: new node
q = deque([root])
qed = set(q)
while q:
# pop
old_node = q.popleft()
# Process
old2new[old_node] = Node(val=old_node.val)
# append children
for old_nei in old_node.neighbors:
if old_nei not in qed:
q.append(old_nei)
qed.add(old_nei)
# clone edge
for old_node in old2new:
for old_nei in old_node.neighbors:
old2new[old_node].neighbors.append(old2new[old_nei])
return old2new[root]
要点
1,2,3,4,5,6,7,8,9
13
27
14
15
16
17
18
20
22
19
21
23
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25
26
28
29
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31
10
11,12
Use qed
as record, no extra dixtionary
"""
# Definition for a Node.
class Node:
def __init__(self, val = 0, neighbors = None):
self.val = val
self.neighbors = neighbors if neighbors is not None else []
"""
class Solution:
def cloneGraph(self, root: 'Node') -> 'Node':
# corner case
if root is None:
return None
# clone nodes by BFS
q = deque([root])
qed = {root: Node(val=root.val)} # key: old node, val: new node
while q:
# pop
old_node = q.popleft()
# append children
for old_nei in old_node.neighbors:
if old_nei not in qed:
q.append(old_nei)
qed[old_nei] = Node(val=old_nei.val) # record enqueue and process
# clone edge
for old_node in qed:
for old_nei in old_node.neighbors:
qed[old_node].neighbors.append(qed[old_nei])
return qed[root]