How should I practice Head-Inserted Linked-List Hash Chain?

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

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Head-Inserted Linked-List Hash Chain

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Problem statement

valueHashes[i] is the already-computed hash of the value inserted on operation i. Insert each new node at the head of a linked list.

A node's stored hash equals its own value hash plus the stored hash of its next node; a missing next node contributes zero. Return the head's stored hash after every insertion.

Do not mutate valueHashes. Every returned value fits in a signed 64-bit integer.

Function

secureHeadHashes(valueHashes: int[]) → long[]

Examples

Example 1

valueHashes = [5,7,2]return = [5,12,14]

The successive head hashes are 5, 7+5, and 2+12.

Example 2

valueHashes = [0,0]return = [0,0]

Zero-valued hashes keep the chain hash at zero.

Example 3

valueHashes = []return = []

No insertions produce no head hashes.

Constraints

0 <= valueHashes.length <= 200000.
0 <= valueHashes[i] <= 10^9.
The sum of all values fits in a signed 64-bit integer.