Clear code, nothing changes
Java note: Overload
Add: Back Reference Heap

Ojbect in heap stores its index in heap. All heap operation maintain the
index.
A GraphNode structure: in complete
implement three stacks using one array (incompleted)
Amazon Interview: frogpath

http://learn.hackerearth.com/question/379/given-a-2-d-mxn-matrix-having-each-value-as-difficulty-for-the-block/#c1858