The K-th Element Problem

Given an array, find the k-th largest (or smallest) element. Approaches:

$1.$ Sort: $O(n \log n)$ time, $O(1)$ extra space.

$2.$ Min-heap of size $k$: $O(n \log k)$ time, $O(k)$ space.

$3.$ Quickselect: $O(n)$ average, $O(n^2)$ worst. The heap approach is effective and reliable. For k-th largest, maintain a min-heap of the $k$ largest elements seen so far.