LeetCode in Kotlin

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.

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

import com_github_leetcode.neighbors.Node

/*
 * Definition for a Node.
 * class Node(var `val`: Int) {
 *     var neighbors: ArrayList<Node?> = ArrayList<Node?>()
 * }
 */
class Solution {
    fun cloneGraph(node: Node?): Node? {
        return cloneGraph(node, HashMap())
    }

    private fun cloneGraph(node: Node?, processedNodes: MutableMap<Node, Node?>): Node? {
        if (node == null) {
            return null
        } else if (processedNodes[node] != null) {
            return processedNodes[node]
        }
        val newNode = Node(node.`val`)
        processedNodes[node] = newNode
        newNode.neighbors = ArrayList()
        for (neighbor in node.neighbors) {
            val clonedNeighbor: Node? = cloneGraph(neighbor, processedNodes)
            if (clonedNeighbor != null) {
                newNode.neighbors.add(clonedNeighbor)
            }
        }
        return newNode
    }
}

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