https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/
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75/*
// Definition for a Node.
class Node {
public int val;
public Node left;
public Node right;
public Node next;
public Node() {}
public Node(int _val) {
val = _val;
}
public Node(int _val, Node _left, Node _right, Node _next) {
val = _val;
left = _left;
right = _right;
next = _next;
}
};
*/
// Straight BFS
class Solution_1 {
public Node connect(Node root) {
if(root==null) return null;
Queue<Node> queue=new LinkedList<>();
queue.offer(root);
while(!queue.isEmpty()){
int size=queue.size();
for(int i=0;i<size;i++){
Node node=queue.poll();
if(i<size-1) node.next=queue.peek();
if(node.left!=null) queue.offer(node.left);
if(node.right!=null) queue.offer(node.right);
}
}
return root;
}
}
// Using previously established next pointers
class Solution_2 {
Node head=null,prev=null,curr;
public void processChild(Node childNode){
if(childNode!=null){
if(prev!=null){
prev.next=childNode;
}else{
head=childNode;
}
prev=childNode;
}
}
public Node connect(Node root) {
if(root==null) return null;
curr=root;
//based on level order traversal
while(curr!=null){
while(curr!=null){//iterate on the current level
if(curr.left!=null) processChild(curr.left);
if(curr.right!=null) processChild(curr.right);
//move to next node
curr=curr.next;
}
//move to next level
curr=head;
head=null;
prev=null;
}
return root;
}
}