Facing cards: Threshold file
Stuck or curious how this works? Visualize Two Pointers ↗
Inputs
readings is a list of integers (numbers with no decimal part). It may be empty, and numbers may repeat unless task 1 says otherwise.
Your tasks
- Create a list
pairSums.readingsis already sorted from smallest to largest. Pair its first and last numbers, then its second and second-last numbers. Keep moving toward the middle. Add the two numbers in each pair and record that sum. If one middle number is left, record it by itself. Keep this pair order inpairSums. - Count the numbers in
pairSumsthat are at leastk(greater than or equal tok). Store the count inatLeastK. - Complete
facingCardsThresholdFileso it returnsatLeastK. Return it, do not print it.
Example
If readings is [-7, 2, 2, 6, 10] and k is 6, then pairSums is [3, 8, 2] and facingCardsThresholdFile returns 1.
Rules
- If
pairSumsis empty, the count is 0. k(a whole number from 1 to 8) is the threshold in task 2: compare each number with it.
Test data
TEST DATA 1: readings is [-6, 0, 3, 4, 4] and k is 6.
TEST DATA 2: readings is [-8, 4, 4, 4] and k is 6.
Examples
Input: readings = [-6,0,3,4,4] k = 6 Output: 0
pairSums is [-2, 4, 3]. Here k is 6. The numbers at least 6 are []. There are 0, so return 0.
Input: readings = [-8,4,4,4] k = 6 Output: 1
pairSums is [-4, 8]. Here k is 6. The numbers at least 6 are [8]. There are 1, so return 1.
Input: readings = [] k = 4 Output: 0
pairSums is []. Here k is 4. The numbers at least 4 are []. There are 0, so return 0.
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.
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 input length. These labels describe how work and memory grow with the input.
Practice focus
Build pairSums 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.