Given a reference of a node in a undirected graph.
Return a (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.
Pseudocode
- to clone a connected undirected graph
- need value of the node
- array of the neighbouring nodes
- initialize a new node with node.val,
- recurse through node.neighbor, and place that neighbor into array
- use visited array, add to array if not visited,
- if visited, just add to neighbor array without recursing (already been there)
Solution
// from solutions
var cloneGraph = function (node) {
const visited = new Array();
if (node == null) {
return node;
}
return cloneHelper(node, visited);
};
var cloneHelper = function (node, visited) {
// console.log(visited, node.val)
const newNode = new Node(node.val);
visited[node.val] = newNode;
for (const neighbor of node.neighbors) {
if (!visited[neighbor.val]) {
const newNeighbor = cloneHelper(neighbor, visited);
newNode.neighbors.push(newNeighbor);
} else {
const newNeighbor = visited[neighbor.val];
newNode.neighbors.push(newNeighbor);
}
}
return newNode;
};
