https://home.cse.ust.hk/~dekai/271/notes/L14/L14.pdf
Lecture 14: Greedy Algorithms
CLRS section 16
Greedy Algorithms: The Fractional Knapsack
Version of September 17, 2016
http://www.cs.ust.hk/mjg_lib/Classes/COMP3711H_Fall16/lectures/Greedy_Knapsack_Handout.pdf
https://web.stanford.edu/class/archive/cs/cs161/cs161.1138/handouts/120%20Guide%20to%20Greedy%20Algorithms.pdf
Guide to Greedy Algorithms