Chain turntable: Positive-ink invoice
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Inputs
head is the first node of a linked list. In examples, [4, 7] means nodes 4 then 7, linked in that order. [] means no nodes. The runner builds the nodes for you.
Your tasks
- Create a list
reversedValues. Reverse the links in the linked list given byhead. Each node has a number in val and a link in next. After the links are reversed, follow the new list from start to end. Record its values in that order. An empty list gives an emptyreversedValues. - Add only the numbers in
reversedValuesthat are greater than 0. Store the sum inpositiveTotal. - Complete
chainTurntablePositiveInkInvoiceso it returnspositiveTotal. Return it, do not print it.
Example
If head is [4, 9, -6, 9, 5], then reversedValues is [5, 9, -6, 9, 4] and chainTurntablePositiveInkInvoice returns 27.
Rules
- Skip 0 and negative numbers.
- If no number is greater than 0, return 0.
Test data
TEST DATA 1: head is [6, 16, -8, 0, 16].
TEST DATA 2: head is [-6, 4, 4, 4].
Examples
Input: head = [6,16,-8,0,16] Output: 38
reversedValues is [16, 0, -8, 16, 6]. Keep [16, 16, 6] and add those numbers. Return 38.
Input: head = [-6,4,4,4] Output: 12
reversedValues is [4, 4, 4, -6]. Keep [4, 4, 4] and add those numbers. Return 12.
Input: head = [] Output: 0
reversedValues is []. Keep [] and add those numbers. Return 0.
Input limits
- 0 <= input size <= 64.
- Answers fit in a signed 32-bit integer: -2,147,483,648 through 2,147,483,647.
- Input numbers have no decimal part. They range from -1,000,000 to 1,000,000. Follow any extra input rules in task 1.
- Linked lists do not loop back to an earlier node. Tree examples list nodes by level; null means a missing child. The runner builds the nodes shown in the examples.
Efficiency goal
Big-O describes how the work or memory needed grows as the input gets larger.
Efficiency goal: time O(n); extra memory, including the helper list, O(n). n is the number of nodes. These labels describe how work and memory grow with the input.
Practice focus
Build reversedValues first, then return exactly what the tasks ask for. Follow the order, keep repeated values when the rule says so, and check the empty case.