2026 April 18 Problems

[daryl...@gmail.com]

Feel free to work on any of the problems you want; we'll have people present their solutions at 11:30.

Please post your solutions to this thread so others can use this as a reference.

Medium and hard problems are carried over from last week.

1315. Sum of Nodes with Even-Valued Grandparent Medium 85.9%

3607. Power Grid Maintenance Medium 56.2%

3812. Minimum Edge Toggles on a Tree Hard 69.0%

We will have a different Zoom meeting that Bhupathi is providing this week:

Here is the meeting url:

https://us05web.zoom.us/j/82553858456?pwd=fnK5Vb0CcfFpv0lnouILjeEs2z2Khc.1 

Full details:

Topic: Leet Code meeting
Time: Mar 28, 2026 10:00 AM Pacific Time (US and Canada)
        Every week on Sat, 110 occurrence(s)
Please download and import the following iCalendar (.ics) files to your calendar system.
Weekly: https://us05web.zoom.us/meeting/tZYocuqgqzMuH9IuHUphHIiZ_4T4IndJLToX/ics?icsToken=DJFc88pL6-me_TneLwAALAAAAA70ShjYgLH6RfEnqUm5LK03v2OgtbXujwlKXRMVgIVWCY9aONPJMCycMlkhyPZ3XSrMVVgXDSYlGF_r7DAwMDAwMQ&meetingMasterEventId=MGJmt5lJTd6mPygcS0hiAQ
Join Zoom Meeting
https://us05web.zoom.us/j/82553858456?pwd=fnK5Vb0CcfFpv0lnouILjeEs2z2Khc.1

Meeting ID: 825 5385 8456
Passcode: 182596

[Anuj Patnaik]

# 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 sumEvenGrandparent(self, root: Optional[TreeNode]) -> int:

sum_ = 0

if(root == None):

return 0

else:

if root.val % 2 == 0:

if root.left != None:

if root.left.left != None:

sum_+= root.left.left.val

if root.left.right != None:

sum_+= root.left.right.val

if root.right != None:

if root.right.left != None:

sum_+= root.right.left.val

if root.right.right != None:

sum_ += root.right.right.val

left_sum = Solution.sumEvenGrandparent(self, root.left)

right_sum = Solution.sumEvenGrandparent(self, root.right)

return left_sum + sum_ + right_sum

[Bhupathi Kakarlapudi]

class Solution:

def sumEvenGrandparent(self, root: Optional[TreeNode]) -> int:

if not root:

return 0

total = 0

# stack entries: (node, parent_val, grandparent_val)

stack = [(root, None, None)]

while stack:

node, parent, grandparent = stack.pop()

if grandparent is not None and grandparent % 2 == 0:

total += node.val

# Push children with updated parent/grandparent context

if node.right:

stack.append((node.right, node.val, parent))

if node.left:

stack.append((node.left, node.val, parent))

return total

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[Rudy W]

# 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 sumEvenGrandparent(self, root: Optional[TreeNode]) -> int:

# intuition: traverse the tree using dfs

# while keeping track of parent and grandparent

if not root:

return 0

sum = 0

# p : parent

# gp : grandparent

def dfs(root, p, gp):

nonlocal sum

if not root:

return

# check if grand parent is not None

# and its value is even

if gp and gp.val % 2 == 0:

sum += root.val

# before traversing down to root's child(s),

# update the parent and grandparent nodes

gp = p # the grandparent is now the parent of current node

p = root # and the parent is current node

dfs(root.left, p, gp)

dfs(root.right, p, gp)

# start from the root node, it has no parent and no grandparent

# so both will be None values

dfs(root, None, None)

return sum

To view this discussion visit https://groups.google.com/d/msgid/leetcode-meetup/CA%2BohYXjFCohiBM%3DjCuMOch4NFfUbbpZ8VQwrWyOnpsYb5MTf1w%40mail.gmail.com.