BRANCH SUMS

 Write a function that takes in a Binary Tree and returns a list of its branch sums ordered from leftmost branch sum to rightmost branch sum.

A branch sum is the sum of all values in a Binary Tree branch. A Binary Tree branch is a path of nodes in a tree that starts at the root node and ends at any leaf node. Each BinaryTree node has an integer value, a left child node, and a right child node. Children nodes can either be BinaryTree nodes themselves or None / null.

OUTPUT -    [15, 16, 18, 10, 11]

// 15 == 1 + 2 + 4 + 8
// 16 == 1 + 2 + 4 + 9
// 18 == 1 + 2 + 5 + 10
// 10 == 1 + 3 + 6
// 11 == 1 + 3 + 7

APPROACH - Take a variable currentSum = 0 and array = [], now traverse the tree using dfs and when you are on root node just append currentSum to array and return, remember when ever you are on any node just add the value of that node to the currentSum.

time : O(n), space : O(n)

branch sums solution

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