leetcode226

遞歸算法：

class Solution {
	ArrayDeque<TreeNode> q=new ArrayDeque<>();
    public TreeNode invertTree(TreeNode root) {
          if(root!=null)
		  {
		     
			TreeNode leftNode=root.left;
			 root.left=invertTree(root.right);
			 root.right=invertTree(leftNode);
		  }
		  return root;
    }
}

非遞歸隊列形式：

class Solution {
    public TreeNode invertTree(TreeNode root) {
        	ArrayDeque<TreeNode> q=new ArrayDeque<>();

		if(root==null) return root;
        	q.offer(root);
		while(!q.isEmpty())
		{
			TreeNode t=q.peek();
			q.poll();
			TreeNode leftRes=t.left;
			
			t.left=t.right;
			t.right=leftRes;
			if(t.left!=null)
			{
				q.offer(t.left);
			}
			if(t.right!=null)
			{
				q.offer(t.right);
			}
		}
		return root;
    }
}