how to handle very large array?

[MichaelBi via Digitalmars-d-learn]

day6 of the advent of code 2021 needs to handle an array of 10^12 
length, or even bigger... plus change elements and append 
elements. normal implementation such as length, appender and ref 
element etc, seems cannot handle that big array? is there any 
alternative data structure or algorithm can handle such large 
array properly? thanks.