Description: 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 val (int) and a list (List[Node]) of its neighbors.
class Node {
public int val;
public List<Node> neighbors;
}
Test case format:
For simplicity sake, 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.
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.
Link: 133. Clone Graph
Examples:
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. Example 4: Input: adjList = [[2],[1]] Output: [[2],[1]]
思路: deep copy，就是要所有node重新创建，关系重新连接好。
class Solution(object): def cloneGraph(self, node): """ :type node: Node :rtype: Node """ return self.dfs(node, dict()) def dfs(self, node, nodes): if not node: return None if node.val in nodes: return nodes[node.val] new = Node(node.val, []) nodes[node.val] = new for n in node.neighbors: new_n = self.dfs(n, nodes) if new_n: new.neighbors.append(new_n) return new
日期: 2021-03-26