Given a reference of a node in a undirected graph, return a (clone) of the graph. Each node in the graph contains a val (int) and a list (List[Node]) of its neighbors.
Example:
Input:
{"$id":"1","neighbors":[{"$id":"2","neighbors":[{"$ref":"1"},{"$id":"3","neighbors":[{"$ref":"2"},{"$id":"4","neighbors":[{"$ref":"3"},{"$ref":"1"}],"val":4}],"val":3}],"val":2},{"$ref":"4"}],"val":1}
Explanation:
Node 1's value is 1, and it has two neighbors: Node 2 and 4.
Node 2's value is 2, and it has two neighbors: Node 1 and 3.
Node 3's value is 3, and it has two neighbors: Node 2 and 4.
Node 4's value is 4, and it has two neighbors: Node 1 and 3.
Note:
The number of nodes will be between 1 and 100.
Since the graph is undirected, if node p has node q as neighbor, then node q must have node p as neighbor too.
You must return the copy of the given node as a reference to the cloned graph.
// Recursive DFS
Node* helper(Node* node, unordered_map<Node*, Node*>& m) {
if (!node) return nullptr;
if (m.count(node)) return m[node];
Node* newNode = new Node(node->val, vector<Node*>());
m[node] = newNode;
for (Node* &neighbor : node->neighbors) {
newNode->neighbors.push_back(helper(neighbor, m));
}
return newNode;
}
Node* cloneGraph(Node* node) { // time: O(n); space: O(n)
unordered_map<Node*, Node*> m;
return helper(node, m);
}
// Iterative BFS
Node* cloneGraph(Node* node) { // time: O(n); space: O(n)
if (!node) return nullptr;
unordered_map<Node*, Node*> m;
Node* copy = new Node(node->val, vector<Node*>());
m[node] = copy;
queue<Node*> q({node});
while (!q.empty()) {
Node* cur = q.front(); q.pop();
for (Node* &neigh : cur->neighbors) {
if (!m.count(neigh)) {
Node* newNode = new Node(neigh->val, vector<Node*>());
m[neigh] = newNode;
q.push(neigh);
}
m[cur]->neighbors.push_back(m[neigh]);
}
}
return copy;
}
The undirected graph is a , which means no repeated edges and no self-loops in the graph.