Tree Level Sums

Problem

Compute the sum of values at each level of a binary tree given in level order.

tree is a LeetCode-style list with None marking missing nodes; the children of index i are at 2*i + 1 and 2*i + 2. Traverse level by level and add the real values.

Return one sum per non-empty level ([] for an empty tree).

Hint

Collect child indices from non-None nodes only; stop when a level contributes nothing.

Test cases

case 1

in: [[1,2,3,4,null,6]]

expected: [1,5,10]

case 2

in: [[]]

expected: []

case 3

in: [[5]]

expected: [5]

case 4

in: [[1,null,3]]

expected: [1,3]

Starter codePython

def level_sums(tree):
    # Your code here
    pass

4 test cases · run your code against them in the editor