How should I practice Minimum-Sum Root-to-Leaf Path?

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Minimum-Sum Root-to-Leaf Path

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Problem statement

Given the root of a nonempty binary tree whose nodes contain signed integers, return the values along a root-to-leaf path whose node-value sum is minimum.

A leaf has no left or right child. If several root-to-leaf paths have the same minimum sum, return the first one encountered by a depth-first traversal that explores each node's left child before its right child.

Return the selected path as an integer array ordered from the root to the leaf.

Function

minimumSumRootToLeafPath(root: TreeNode) → int[]

Examples

Example 1

root = [1,2,3,4,5,6,7]return = [1,2,4]

The four root-to-leaf sums are 7, 8, 10, and 11. The minimum is 1 + 2 + 4 = 7.

Example 2

root = [5,1,1]return = [5,1]

Both leaves produce a sum of 6. The left leaf is visited first, so the left path is returned.

Example 3

root = [10,-5,2,null,-10]return = [10,-5,-10]

The left path has sum -5, while the right path has sum 12. Negative values therefore make the deeper left path optimal.

Constraints

The tree contains between 1 and 100000 nodes.
-1000000000 <= node.val <= 1000000000.
Every root-to-leaf sum fits in a signed 64-bit integer.
The input is a valid finite binary tree encoded in level order with explicit null children.