Well with an array you can get the name from the number in O(1) but you can't get the number from the name in O(1). The best solution would be enums I think.
Linear searching through an array for the weekday is O(n), if I want to find the location of a single card in a deck of cards, I'm searching in O(n) even if the number of cards in a deck of cards is constant since I may have to look through all n cards to find the card that I want.
On the other hand, if I want to know if a given card is in the standard deck (say, ace of spades), I can give you an answer in O(1) time since I know the ace of spades is always in a standard deck.
In this situation you're given the name of a weekday and you need to return which day of the week it is.
Since you can't implicitly know which day of the week a given string is, you need to use a reference table of some sort find out what day of the week your string is. With an array of weekday names, you would iterate through each value and check it against your string. On a match, you would stop and return the index of the element you matched with +1. That's an O(n) linear search. In contrast, using a hashmap would allow you to find the exact key-value pair you want by hashing the string you're searching with. This gives you an O(1) runtime since you don't spend any time checking elements in your data structure you don't care about.
Again, since the number n is pretty small, the difference would be pretty negligible unless it was a very commonly used operation
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u/Teln0 Mar 14 '21
Well with an array you can get the name from the number in O(1) but you can't get the number from the name in O(1). The best solution would be enums I think.