Problem
Return the k-th smallest value of the list (k counts from 1). Quickselect finds it in average O(n) time without sorting everything.
Implement kth_smallest(numbers, k).
Input
numbers: The list of integers. k: Which smallest value to return, starting at 1.
Output
Return the k-th smallest value.
Constraints
1 ≤ k ≤ length ≤ 200,000
Examples
Example 1
Input:
k = 3
numbers = [7, 10, 4, 3, 20, 15]
Expected output:
expected = 7Input:
long long k = 3;
std::vector<long long> numbers = {7, 10, 4, 3, 20, 15};
Expected output:
long long expected = 7;Input:
long k = 3;
long[] numbers = new long[] {7, 10, 4, 3, 20, 15};
Expected output:
long expected = 7;Explanation
Sorted: 3, 4, 7, 10, 15, 20; the 3rd smallest is 7.
Example 2
Input:
k = 2
numbers = [5, 5, 1]
Expected output:
expected = 5Input:
long long k = 2;
std::vector<long long> numbers = {5, 5, 1};
Expected output:
long long expected = 5;Input:
long k = 2;
long[] numbers = new long[] {5, 5, 1};
Expected output:
long expected = 5;Explanation
Sorted: 1, 5, 5; the 2nd smallest is 5 (duplicates count).
References
This challenge is adapted for CodeUtility. Follow the statement and constraints above.