DEV Community


Posted on


LeetCode 133. Clone Graph (javascript solution)


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 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.


Time Complexity : O(n)
Space Complexity: O(n)

// DFS approach
var cloneGraph = function(node) {
    // Nodes we have already copied
    const visited = {};

    // DFS function to copy graph
    const dfs = (node) => {
        if (!node) return node;
        // If we have seen this node before, return it
        if (visited[node.val]!=null) return visited[node.val];

        // Create base for copied node
        const root = new Node(node.val);
        // Add this copied node to group of nodes we hav copied
        visited[node.val] = root;

        // Add copied neighbors to the current copied node
        node.neighbors.forEach(n => root.neighbors.push(dfs(n)))
        return root;

    // Return new copied graph
    return dfs(node);
Enter fullscreen mode Exit fullscreen mode

Top comments (1)

qurashieman profile image
Tuba Inam

I found that solution is very popular and helpful: