C#•3y ago

My head hurts understanding this LINQ

static IEnumerable<string> serializeToEnumerable(TreeNode root)
            => root is null 
                ? new string[] { String.Empty } 
                : serializeToEnumerable(root.left)
                        .Concat(serializeToEnumerable(root.right))
                        .Prepend(root.val.ToString());

static IEnumerable<string> serializeToEnumerable(TreeNode root)
            => root is null 
                ? new string[] { String.Empty } 
                : serializeToEnumerable(root.left)
                        .Concat(serializeToEnumerable(root.right))
                        .Prepend(root.val.ToString());

18 Replies

KidKai25OP•3y ago

I thought I knew Linq

Saber•3y ago

not really much linq happening here. what is confusing

KidKai25OP•3y ago

I mean I never saw recursion + Concat + Prepend this way really cool catpog

I couldn't come up with this?

Saber•3y ago

i don't know. might not have a good enough understanding of how to solve a problem and the overall knowledge of how things can play together

KidKai25OP•3y ago

thank you. You are awesome as always.

TheBoxyBear•3y ago

Converting a TreeNode to a set of strings. ?: is a ternary expression a ? b : c returning either b or c depending on the value of bool a If left and right have two way references, this might cause a stakcoverflow however

KidKai25OP•3y ago

my one issue in understanding was the calling of recursive methods like again inside Concat

TheBoxyBear•3y ago

Considering nodes A B and C from left to right

KidKai25OP•3y ago

Need to wrap my head around more.

TheBoxyBear•3y ago

Resurcion to serialize all the nodes to the left and right Not just the one node

KidKai25OP•3y ago

it's a binary tree though

TheBoxyBear•3y ago

Though I'm worried it might loop endlessly. Say if you were to serialize node B, it starts by serializing A but by serializing A, it also serializes B as part of .Concat(serializeToEnumerable(root.right)) Then it's fine So left and right are the branches from the node, right?

KidKai25OP•3y ago

yup

TheBoxyBear•3y ago

Trees and recursion go hand in hand Continuing to navigate a tree from a node is the same as navigating a full tree with the same node as root

KidKai25OP•3y ago

yes right

TheBoxyBear•3y ago

So the result for a node is [This, Left, Right]

KidKai25OP•3y ago

yes and this is called PreOrder way I get it now, thank you BoxyBear and Saber 🙂

TheBoxyBear•3y ago

Gaming

Programming

My head hurts understanding this LINQ