1、题目
Invert a binary tree.
Example:
Input:
4
/ \
2 7
/ \ / \
1 3 6 9 Output:
4
/ \
7 2
/ \ / \
9 6 3 1 Trivia: This problem was inspired by this original tweet by Max Howell:
2、思路
如果该节点不是叶子节点，就交换该节点的左右节点，然后递归反转左子树和右子树
3、递归实现
public TreeNode invertTree(TreeNode root) {
if (root == null)
{
return root;
}
if (root.left != null || root.right != null)
{
TreeNode node = new TreeNode(0);
node = root.left;
root.left = root.right;
root.right = node;
// 反转左子树
if (root.left != null)
{
invertTree(root.left);
}
// 反转右子树
if (root.right != null)
{
invertTree(root.right);
}
}
return root;
}
