// 后序遍历
void postOrder(TreeNode root) {
if(root == null){
return;
}
postOrder(root.left);
postOrder(root.right);
System.out.print(root.val+" ");
}
// 后序遍历
void postOrder(TreeNode root) {
if(root == null){
return;
}
postOrder(root.left);
postOrder(root.right);
System.out.print(root.val+" ");
}