LeetCode Binary Tree Pruning Explained - Java

Preparing For Your Coding Interviews? Use These Resources
————————————————————

Other Social Media
----------------------------------------------

Show Support
------------------------------------------------------------------------------

#coding #programming #softwareengineering

[ItsJbirdJustin]

This needs to check if root.left is null, root.right is null, and root.val is 0 to return null instead of [0]

[nero-kun-here]

TreeNode* pruneTree(TreeNode* root) {
if(root == NULL)
return NULL;
root->left = pruneTree(root->left);
root->right = pruneTree(root->right);
if(root->val == 0 && root->left == NULL && root->right == NULL)
root=NULL;
return root;
}

**This solution is quite easy to implement**

[romirpatney]

*Video Summary*
Question: Delete/prune a sub-tree if it doesn't contain a 1.
*Something not highlighted but important:*
You use POSTORDER tree traversal to traverse and check. "post" i.e. root node is traversed post exploration i.e. root node is explored in the end. Why? Because you want to check if a subtree's subtree has something or not (in this case a 1), only after which you can decide to prune or not, in which case you use postorder.

[QueenCoder]

That girl speaking hindi in background 😘

[TechOnScreen]

the solution fails for below input on leetcode.
[0, null, 0, 0, 0]

[jackedelic]

"Sorry bout the volume there's ppl talking we're in the LIBRARY" lol

[amanmalhotra]

class Solution {
public TreeNode pruneTree(TreeNode root) {
if(root == null) return null;
root.left = pruneTree(root.left);
root.right = pruneTree(root.right);
if(root.left == null && root.right == null && root.val == 0){
return null;
}
return root;
}
}

[rupaldesai]

on line number 13, the helper method returns a boolean value, even tho the value is not caught how it is complied successfully?

[sameer]

I think most of the people in the library are Indians😂😂

[god-speed]

If root==none:
Return
Fn(root.left)
Fn(root.right)
If root. Left==0 and root. Right==0 and root. Val==0:
Root==none


Why this is not working???

[unseenworld]

TreeNode* pruneTree(TreeNode* root) {
if(root!=NULL){
root->left = pruneTree(root->left);
root->right = pruneTree(root->right);
if(!root->left && !root->right && root->val==0)
return NULL;
}
return root;
}

[downey]

if(root==null) return null;


if(root.val!=1 && root.left==null && root.right==null) return null;
return root;