133. Clone Graph

Clone an undirected graph. Each node in the graph contains a 

label

 and
a list of its 

neighbors

.

Solution 1 BFS

//BFS
public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
if(node == null){
return null;
}
Queue<UndirectedGraphNode> q = new LinkedList<UndirectedGraphNode>();
Map<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
map.put(node,new UndirectedGraphNode(node.label));
q.add(node);
while(!q.isEmpty()){
UndirectedGraphNode temp = q.poll();
for(UndirectedGraphNode neighbour : temp.neighbors){
if(!map.containsKey(neighbour)){
map.put(neighbour, new UndirectedGraphNode(neighbour.label));
q.add(neighbour);
}
map.get(temp).neighbors.add(map.get(neighbour));
}
}
return map.get(node);
}

Solution 2 DFS Recursive
//DFS
Map<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
public UndirectedGraphNode cloneGraph2(UndirectedGraphNode node) {
if(node == null){
return null;
}
if(map.containsKey(node)){
return map.get(node);
}
UndirectedGraphNode temp = new UndirectedGraphNode(node.label);
map.put(node, temp);
for(UndirectedGraphNode n : node.neighbors){
temp.neighbors.add(cloneGraph2(n));
}
return temp;
}

Solution 3 DFS Iterative
//Iterative DFS
public UndirectedGraphNode cloneGraph3(UndirectedGraphNode root) {
if (root == null) return null;

// use a stack to help DFS
Stack<UndirectedGraphNode> stack = new Stack<UndirectedGraphNode>();
stack.push(root);

// use a map to save cloned nodes
Map<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();

// clone the root
map.put(root, new UndirectedGraphNode(root.label));

while (!stack.isEmpty()) {
UndirectedGraphNode node = stack.pop();

// handle the neighbors
for (UndirectedGraphNode neighbor : node.neighbors) {
if (!map.containsKey(neighbor)) {
// clone the neighbor
map.put(neighbor, new UndirectedGraphNode(neighbor.label));
// add it to the next level
stack.push(neighbor);
}

// copy the neighbor
map.get(node).neighbors.add(map.get(neighbor));
}
}

return map.get(root);
}