Clone Graph

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.

 

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]]

 

Constraints:

• 1 <= Node.val <= 100
• Node.val is unique for each node.
• Number of Nodes will not exceed 100.
• There is no repeated edges and no self-loops in the graph.
• The Graph is connected and all nodes can be visited starting from the given node.

Solution(javascript)

/*
 * @lc app=leetcode id=133 lang=javascript
 *
 * [133] Clone Graph
 */

// @lc code=start
/**
 * // Definition for a Node.
 * function Node(val,neighbors) {
 *    this.val = val;
 *    this.neighbors = neighbors;
 * };
 */
/** BFS, 存储的结构类似 138
 * @param {Node} node
 * @return {Node}
 */
const cloneGraph = function (node) {
  if (!node) {
    return null
  }
  const copy = node2 => new Node(node2.val, [])
  const map = new Map()
  map.set(node, copy(node))
  let current = [node]
  while (current.length > 0) {
    const next = []
    current.forEach((node2) => {
      (node2.neighbors || []).forEach((neighbor) => {
        if (!map.get(neighbor)) {
          next.push(neighbor)
          map.set(neighbor, copy(neighbor))
        }
      })
    })
    current = next
  }
  for (const node2 of map.keys()) {
    const cloneNode = map.get(node2);
    (node2.neighbors || []).forEach((neighbor) => {
      cloneNode.neighbors = cloneNode.neighbors || []
      cloneNode.neighbors.push(map.get(neighbor))
    })
  }
  return map.get(node)
}
// @lc code=end