Chain inspection: First qualifying slip
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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
values.headis the first node of a linked list. A node holds a number in val and a link to the next node in next. Follow next until there are no more nodes. Record each val in order. The list has no loops. An empty list gives an emptyvalues. - Read
valuesfrom left to right. Find the first number that is at leastkand store that number, not its position, infirstMatch. - Complete
chainInspectionFirstQualifyingSlipso it returnsfirstMatch. Return it, do not print it.
Example
If head is [6, -4, 2, 1, 6] and k is 2, then values is [6, -4, 2, 1, 6] and chainInspectionFirstQualifyingSlip returns 6.
Rules
- If no number is at least
k, return -1. k(a whole number from 1 to 8) is the threshold in task 2: compare each number with it.
Test data
TEST DATA 1: head is [18, 18, 14, 0, -2] and k is 6.
TEST DATA 2: head is [3, 3, 3, -7] and k is 7.
Examples
Input: head = [18,18,14,0,-2] k = 6 Output: 18
values is [18, 18, 14, 0, -2]. Here k is 6. The first number at least 6 is 18. Return that value.
Input: head = [3,3,3,-7] k = 7 Output: -1
values is [3, 3, 3, -7]. Here k is 7. No number is at least 7, so return -1.
Input: head = [] k = 7 Output: -1
values is []. Here k is 7. No number is at least 7, so return -1.
Input limits
- 0 <= input size <= 64.
- k is a whole number from 1 to 8. 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 values 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.