Desafío de programación K-th Smallest Element

Problema

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).

numbers: The list of integers. k: Which smallest value to return, starting at 1.

Return the k-th smallest value.

1 ≤ k ≤ length ≤ 200,000

Ejemplo 1

Entrada:
k = 3
numbers = [7, 10, 4, 3, 20, 15]

Salida esperada:
expected = 7

Entrada:
long long k = 3;
std::vector<long long> numbers = {7, 10, 4, 3, 20, 15};

Salida esperada:
long long expected = 7;

Entrada:
long k = 3;
long[] numbers = new long[] {7, 10, 4, 3, 20, 15};

Salida esperada:
long expected = 7;

Sorted: 3, 4, 7, 10, 15, 20; the 3rd smallest is 7.

Ejemplo 2

Entrada:
k = 2
numbers = [5, 5, 1]

Salida esperada:
expected = 5

Entrada:
long long k = 2;
std::vector<long long> numbers = {5, 5, 1};

Salida esperada:
long long expected = 5;

Entrada:
long k = 2;
long[] numbers = new long[] {5, 5, 1};

Salida esperada:
long expected = 5;

Sorted: 1, 5, 5; the 2nd smallest is 5 (duplicates count).

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