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.
tree = 1
/ \
2 3
/ \ / \
4 5 6 7
/ \ /
8 9 10
Sample 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
Hints
Hint 1
Try traversing the Binary Tree in a depth-first-search-like fashion.
Hint 2
Recursively traverse the Binary Tree in a depth-first-search-like fashion, and pass a running sum of the values of every previously-visited node to each node that you're traversing.
Hint 3
As you recursively traverse the tree, if you reach a leaf node (a node with no "left" or "right" Binary Tree nodes), add the relevant running sum that you've calculated to a list of sums (which you'll also have to pass to the recursive function). If you reach a node that isn't a leaf node, keep recursively traversing its children nodes, passing the correctly updated running sum to them.
Optimal Space & Time Complexity
O(n) time | O(n) space - where n is the number of nodes in the Binary Tree