0133. Clone Graph.js

// 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.

// 1) BFS
/**
 * // Definition for a Node.
 * function Node(val, neighbors) {
 *    this.val = val === undefined ? 0 : val;
 *    this.neighbors = neighbors === undefined ? [] : neighbors;
 * };
 */

/**
 * @param {Node} node
 * @return {Node}
 */
const cloneGraph = function(node) {
  if (!node) {
    return null
  }
  const copy = new Node(node.val, [])
  const visited = new Map()
  visited.set(node, copy)
  const list = [node]
  while (list.length) {
    const cur = list.shift()
    for (const neighbor of cur.neighbors) {
      if (!visited.has(neighbor)) {
        visited.set(neighbor, new Node(neighbor.val, []))
        list.push(neighbor)
      }
      visited.get(cur).neighbors.push(visited.get(neighbor))
    }
  }
  return copy
}