Same Tree LeetCode

[fathom meteor]

What am I doing wrong here

[silver dock]

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[fathom meteor]

class Solution {
    List<Integer> treeElements1 = new ArrayList<>();
    List<Integer> treeElements2 = new ArrayList<>();

    public boolean isSameTree(TreeNode p, TreeNode q) {
        inOrderTraversal(p, treeElements1);
        inOrderTraversal(q, treeElements2);
        System.out.println("tree 1");
        printList(treeElements1);
        System.out.println("tree 2");
        printList(treeElements2);
        if (treeElements1.equals(treeElements2))
            return true;
        else
            return false;
    }

    public static void printList(List<Integer> list) {
        for (Integer element : list) {
            System.out.println(element);
        }
    }

    public void inOrderTraversal(TreeNode root, List<Integer> list) {
        if (root != null) {

            if (root.left != null) {
                inOrderTraversal(root.left, list);
            }
            list.add(root.val);
            if (root.right != null) {
                inOrderTraversal(root.right, list);
            }

        }
        if(root = null){
            
        }
    }
}

Failing test case

[worn socket]

You're flattening the trees into Lists, then comparing the Lists

It could work if you ensured the List you flatten to were canonically representing the trees, but you don't. You produce the same list with a missing left node and a missing right node.

[fathom meteor]

yah how to canonically represent the tree?

[worn socket]

You could do it the same as they do in the input part

Here when there is a missing node in the middle they insert null

[fathom meteor]

yah I tried that then also it generated the same tree

[worn socket]

The same list you mean?

[fathom meteor]

yah it turned out a same list

[worn socket]

That's not an attempt to add nulls. You just modified where you insert the root

[fathom meteor]

alright I figured it out

public void inOrderTraversal(TreeNode root, List<Integer> list) {
        if (root != null) {

            if (root.left != null) {
                inOrderTraversal(root.left, list);

            } else {
                list.add(null);
            }
            list.add(root.val);
            if (root.right != null) {
                inOrderTraversal(root.right, list);

            } else {
                list.add(null);
            }

            inOrderTraversal(root.right, list);

        }

    }

[worn socket]

I just noticed your list is not like the one they put in input box. I'm not sure it will be canonical this way

[fathom meteor]

is the better approach?

[fathom meteor]

This reaches till the end of the leaf node of one of the tree right
Then it check if the values are null, one is not null or no even

[worn socket]

I mean, it's the most direct approach. Trees are recursive structures, so it checks recursively and directly.