Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.
[3,2,1,5,6,4]and k = 2 Output: 5
[3,2,3,1,2,4,5,5,6]and k = 4 Output: 4
You may assume k is always valid, 1 ≤ k ≤ array's length.