Android Question Find key from value in map or list

[kenten123]

Is there any way to do a reverse lookup in a map (or list). Given that I know a Value is there a way to find the corresponding Key directly - that is, without iterating over all indexes ?

Thanks for any help.

Ken

 

[Erel]

You can use List.IndexOf or iterate over the values in a Map. The operation cost is the same - O(n).

If the Map is very large then you can use two maps. One with the keys as keys and one with the values as keys.

 

[kenten123]

Thanks. I'll go with two maps