Problems
Find min & max from a vector in 1.5 * N comparisons
More bs
Find composed word
Bit manipulation
External sorting:
* read data in chunks
* sort chunks
* merge chunks

k-way merging:
a. merge 2 chunks then result with 3rd chunk etc
b. go in parallel with k-indexes
c. use a min-heap:
- create heap from first elements of each list
- extract min
- insert new element in min-heap