Discussion 10: Heaps
Lecture note: http://homepages.math.uic.edu/~jan/mcs360/expression_trees.pdf

4 2 3 1 5 6

.	4
x

.	4
2		x

.		4
	2		3
x

.		4
	2		3
1	x

.		4
	2		3
1	5

-> 		4
	5		3
1	2

-> 		5
	4		3
1	2		x

.		5
	4		3
1	2		6

->		5
	4		6
1	2		3

->		6
	4		5
1	2		3

Pop from this heap:
-: 6
->		3
	4		5
1	2		
-> heapify: 
->		5
	4		3
1	2

-: 6 5 
->		2
	4		3
1	
-> heapify: 
		4
	2		3
1
-: 6 5 4
		1
	2		3
	
-> 		3
	2		1
	
-: 6 5 4 3 
-> 		1
	2
-> 		2
	1
-: 6 5 4 3 2

-> 1

-: 6 5 4 3 2 1