[leetcode]Populating Next Right Pointers in Each Node - java 广度遍历

这题没啥难度，主要是仔细了

/**

 * Definition for binary tree with next pointer.

 * public class TreeLinkNode {

 *     int val;

 *     TreeLinkNode left, right, next;

 *     TreeLinkNode(int x) { val = x; }

 * }

 */

public class Solution {

   public void connect(TreeLinkNode root) {

        if(root == null){

            return;

        }

        int k = 0;

        int length = (int)Math.pow(2, k);

        LinkedList<TreeLinkNode> queue = new LinkedList<TreeLinkNode>();

        queue.add(root);

        TreeLinkNode preNode = null;

        while (!queue.isEmpty()){

            TreeLinkNode node = queue.remove();

            if(node.left != null){

                queue.add(node.left);

            }

            if(node.right!=null){

                queue.add(node.right);

            }

            if(preNode != null){

                preNode.next=node;

            }

            if(length == 1){

                length = (int)Math.pow(2, ++k);

                node.next=null;

                preNode = null;

            }else{

                preNode = node;

                length--;

            }

        }

    }

}