Which of the following sorting algorithms has the lowest worst-case complexity?

Consider the DAG with $$V = \{1,2,3,4,5,6\}$$, shown below. Which of the following is NOT a topological ordering?

An element in an array X is called a leader if it is greater than all elements to the right of it in X. The best algorithm to find all leaders in an array

In a binary max heap containing n numbers, the smallest element can be found in time