133.clone-graph.java

/*
 * @lc app=leetcode id=133 lang=java
 *
 * [133] Clone Graph
 *
 * https://leetcode.com/problems/clone-graph/description/
 *
 * algorithms
 * Medium (35.06%)
 * Likes:    1907
 * Dislikes: 1399
 * Total Accepted:    354.1K
 * Total Submissions: 1M
 * Testcase Example:  '[[2,4],[1,3],[2,4],[1,3]]'
 *
 * 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.
 * 
 * 
 */

// @lc code=start
/*
// Definition for a Node.
class Node {
    public int val;
    public List<Node> neighbors;
    
    public Node() {
        val = 0;
        neighbors = new ArrayList<Node>();
    }
    
    public Node(int _val) {
        val = _val;
        neighbors = new ArrayList<Node>();
    }
    
    public Node(int _val, ArrayList<Node> _neighbors) {
        val = _val;
        neighbors = _neighbors;
    }
}
*/
import java.util.*;
class Solution {
    public Node cloneGraph(Node node) {
         Node result = cloned(node);
         return result;
        
    }

    public Node cloned(Node node){
        
        if(node == null){
            return null;
        }

        Map<Node,Node> map = new HashMap<Node,Node>();
        Queue<Node> queue = new LinkedList<>();
        
        queue.add(node);

        map.put(node,new Node(node.val));

        while(!queue.isEmpty()){

            Node temp = queue.poll();

            Node n1clone = map.get(temp);

            if(temp.neighbors!=null){
                for(Node t : temp.neighbors){

                    Node n2clone = map.get(t);
                    if(n2clone==null){
                        queue.add(t);
                        n2clone = new Node(t.val);
                        map.put(t,n2clone);
                    }
                    n1clone.neighbors.add(n2clone);
                }
            }

        }

        return map.get(node);

        }
    }
// @lc code=end