Clone Graph - LeetCode

Description

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<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.

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.

Code

/*
// Definition for a Node.
class Node {
public:
    int val;
    vector<Node*> neighbors;
    Node() {
        val = 0;
        neighbors = vector<Node*>();
    }
    Node(int _val) {
        val = _val;
        neighbors = vector<Node*>();
    }
    Node(int _val, vector<Node*> _neighbors) {
        val = _val;
        neighbors = _neighbors;
    }
};
*/
 
class Solution {
public:
    unordered_map<Node*, Node*> mp;
 
    Node* cloneGraph(Node* node) {
        if(!node) return nullptr;
        if(mp.find(node) == mp.end()) {
            mp[node] = new Node(node->val, {});
            for(auto neighbor: node->neighbors) {
                mp[node]->neighbors.push_back(cloneGraph(neighbor));
            }
        }
 
        return mp[node];
    }
 
};

/*
// Definition for a Node.
class Node {
public:
    int val;
    vector<Node*> neighbors;
    Node() {
        val = 0;
        neighbors = vector<Node*>();
    }
    Node(int _val) {
        val = _val;
        neighbors = vector<Node*>();
    }
    Node(int _val, vector<Node*> _neighbors) {
        val = _val;
        neighbors = _neighbors;
    }
};
*/
 
class Solution {
public:
    unordered_map<Node*, Node*> v_map;
    Node* cloneGraph(Node* node) {
        if(!node) return node;
        
        if(v_map.find(node) != v_map.end()) {
            return v_map[node];
        }
 
        Node* new_head = new Node(node->val);
        v_map[node] = new_head;
 
        int n = node->neighbors.size();
        vector<Node*> new_neighbors(n);
        for(int i = 0; i < n; i++) {
            new_neighbors[i] = cloneGraph(node->neighbors[i]);
        }
        new_head->neighbors = new_neighbors;
 
        return new_head;
 
    }
};

Source

• Clone Graph - LeetCode