翻转一棵二叉树（非递归版本）

public class Solution {
    /**
     * @param root: a TreeNode, the root of the binary tree
     * @return: nothing
     */
    public void invertBinaryTree(TreeNode root) {
        // write your code here
        if(root == null){
            return;
        }
        Queue<TreeNode> queue = new LinkedList<TreeNode>();
        queue.offer(root);
        while(!queue.isEmpty()){
            int size = queue.size();
            for(int i = 0; i < size; i++){
                TreeNode node = queue.poll();
                TreeNode temp = node.left;
                node.left = node.right;
                node.right = temp;
                if(node.left != null){
                    queue.offer(node.left);
                }
                if(node.right != null){
                    queue.offer(node.right);
                }
            }
        }
    }
}

解题思路：
通过队列将每个节点的左右子节点翻转