226. Invert Binary Tree

 

 

Solution1: 

class Solution {

    public TreeNode invertTree(TreeNode root) {

        if (root == null) return null;

        TreeNode tmp = root.left;

        root.left = invertTree(root.right);

        root.right = invertTree(tmp);

        return root;

    }

}

 

Solution2: //迭代的方法

class Solution {

    public TreeNode invertTree(TreeNode root) {

        if (root == null) return null;

        Queue<TreeNode> queue = new LinkedList<>();

        queue.offer(root);

        while (!queue.isEmpty()) {

            TreeNode node = queue.poll();

            TreeNode left = node.left;

            node.left = node.right;

            node.right = left;

            if (node.left != null) {

               queue.offer(node.left);

            }

            if (node.right != null) {

               queue.offer(node.right);

            }

        }

        return root;

    }

}