Heaps and Heapsort - Find the 7'th biggest value in a min heap by $O(1)$
O(1) means: You need to do this with a fixed number of operations. Basically, write code without a loop. That's not difficult. It's a lot of code, but a fixed amount of code. 

Look at your heap as if it was a binary tree. You want the 7th largest item in your tree. That's the sixth largest of the subtrees L and R. If the item at L is smaller than the item at R, it's the fifth largest item in the subtrees L, RL and RR, otherwise the fifth largest item in the subtrees R, LL and LR. And so on..