Dynamic shrinking. With the array implementations of stack and queue, we doubled the size of the array when it wasn’t big enough to store the next element. If we perform a number of doubling operations, and then delete a lot of elements, we might end up with an array that is much bigger than necessary. Implement the following strategy: whenever the array is 1/4 full or less, shrink it to half the size. Explain why we don’t shrink it to half the size when it is 1/2 full or less.
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Stacks at PU
https://algs4.cs.princeton.edu/13stacks/
Stacks
http://algorithms.mrseliasclasses.org/2-stacks-problems/