Java Community | Help. Code. Learn.•5mo ago

Same Tree LeetCode

What am I doing wrong here

17 Replies

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Rag...JN 🌌 🦡 👽 💰 🐊OP•5mo ago

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){
            
        }
    }
}

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){
            
        }
    }
}

Rag...JN 🌌 🦡 👽 💰 🐊OP•5mo ago

Failing test case

Kyo-chan•5mo ago

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.

Rag...JN 🌌 🦡 👽 💰 🐊OP•5mo ago

yah how to canonically represent the tree?

Kyo-chan•5mo ago

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

Rag...JN 🌌 🦡 👽 💰 🐊OP•5mo ago

yah I tried that then also it generated the same tree

Kyo-chan•5mo ago

The same list you mean?

Rag...JN 🌌 🦡 👽 💰 🐊OP•5mo ago

yah it turned out a same list

Kyo-chan•5mo ago

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

Rag...JN 🌌 🦡 👽 💰 🐊OP•5mo ago

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);

        }

    }

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);

        }

    }

Kyo-chan•5mo ago

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

Rag...JN 🌌 🦡 👽 💰 🐊OP•5mo ago

is the better approach?

Rag...JN 🌌 🦡 👽 💰 🐊OP•5mo ago

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

Kyo-chan•5mo ago

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

JavaBot•5mo ago

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