def kth_largest_in_an_array(numbers, k):

    def helper(numbers,start,end,index):

        pivot=random.randint(start,end)
        numbers[start],numbers[pivot]=numbers[pivot],numbers[start]

        left = start
        mid = start
        right = end

        while mid <= right:
            if numbers[mid] < numbers[start]:
                left = left + 1
                numbers[left], numbers[mid] = numbers[mid], numbers[left]
                mid = mid+1
            elif numbers[mid] == numbers[start]:
                mid = mid+1
            else:
                numbers[mid], numbers[right] = numbers[right], numbers[mid]
                right = right-1

        numbers[start], numbers[left] = numbers[left], numbers[start]

        if left <= index and index <= right:
            return
        elif index < left:
            helper(numbers,start,left-1,index)
        elif index > right:
            helper(numbers,right+1,end,index)


    helper(numbers,0,len(numbers)-1,len(numbers)-k)
    result = numbers[len(numbers)-k]
    return result