How should I practice Mode of a Ternary Search Tree?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Google phone screen problems in FastPrep.

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FastPrep tags this as a Google phone screen coding practice problem when the problem catalog has that company and stage context.

Mode of a Ternary Search Tree

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Problem statement

A ternary search tree is encoded by a node table nodes. Row i is [value, leftIndex, middleIndex, rightIndex], row 0 is the root, and -1 means that a child is absent.

Every node in a left subtree has a smaller value than its parent.
Every node in a middle subtree has the same value as its parent.
Every node in a right subtree has a larger value than its parent.

Return the mode: the value that occurs most often. If several values have the same highest frequency, return the smallest one.

Function

ternaryTreeMode(nodes: int[][]) → int

Examples

Example 1

nodes = [[5,1,2,3],[3,-1,-1,-1],[5,-1,4,-1],[8,-1,-1,-1],[5,-1,-1,-1]]return = 5

The value 5 occurs three times.

Example 2

nodes = [[2,1,2,3],[1,-1,-1,-1],[2,-1,-1,-1],[3,-1,-1,-1]]return = 2

The root value occurs twice.

Example 3

nodes = [[7,-1,-1,-1]]return = 7

A one-node tree has that node's value as its mode.

Constraints

1 <= nodes.length <= 200000.
Each row has exactly four integers.
Every nonnegative child index is valid, every node is reachable exactly once from row 0, and the stated ternary-search-tree invariant holds.