LeetCode in TypeScript

133. Clone Graph

Medium

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.

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:

• The number of nodes in the graph is in the range [0, 100].
• 1 <= Node.val <= 100
• Node.val is unique for each node.
• There are 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

class Node {
    val: number
    neighbors: Node[]

    constructor(val: number = 0, neighbors: Node[] = []) {
        this.val = val
        this.neighbors = neighbors
    }

    toString(): string {
        const result: string[] = []
        for (const node of this.neighbors) {
            if (node.neighbors.length === 0) {
                result.push(node.val.toString())
            } else {
                const result2: string[] = []
                for (const nodeItem of node.neighbors) {
                    result2.push(nodeItem.val.toString())
                }
                result.push(`[${result2.join(',')}]`)
            }
        }
        return `[${result.join(',')}]`
    }
}

function cloneGraph(node: Node | null): Node | null {
    const processedNodes = new Map<Node, Node>()
    return cloneGraphHelper(node, processedNodes)
}

function cloneGraphHelper(node: Node | null, processedNodes: Map<Node, Node>): Node | null {
    if (node === null) {
        return null
    }
    if (processedNodes.has(node)) {
        return processedNodes.get(node)!
    }
    const newNode = new Node(node.val)
    processedNodes.set(node, newNode)
    for (const neighbor of node.neighbors) {
        const clonedNeighbor = cloneGraphHelper(neighbor, processedNodes)
        if (clonedNeighbor !== null) {
            newNode.neighbors.push(clonedNeighbor)
        }
    }
    return newNode
}

export { Node, cloneGraph }

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