Delete leaves with a given value

We will use recursion to solve this problem. If the current node is a leaf and its value is the target value, we will return None. Otherwise, we will recursively call the function on the left and right child. If the left child is None, we will return the right child, and vice versa. Finally, we will return the current node.

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right

class Solution:
    def removeLeafNodes(self, root: Optional[TreeNode], target: int) -> Optional[TreeNode]:
        if root.left: 
            root.left = self.removeLeafNodes(root.left, target)
        if root.right: 
            root.right = self.removeLeafNodes(root.right, target)

        return None if root.left == root.right == None and root.val == target else root

Time Complexity: O(n)
Space Complexity: O(h), h is the height of the tree