Question:- 181B - Сколько троек
Question
Solution that got accepted-: 178183074
Solution that got rejected-: 178183367
Other solution using same concept
Summary: The logic of both code is same, I've tried using HashMap and HashSet but the solution does not work.
I do not understand why don't the code using HasHmap/HashSet work.
Any help is appreciated.
Thank you.
String-based HashSet? Bad idea... The string formed by the numbers 1 and 23 is the same as the string formed by the numbers 12 and 3 — you can guess how this can go terribly wrong.
A HashMap / HashSet solution is easily possible by using a unique concatenation of numbers. Example: if the numbers are between -1000 and 1000, then you can artificially add 1000 to make them positive and then set: key = number1 * 2001 + number2. Thus, the key's remainder when divided by 2001 is definitely number2+1000, and its quotient is definitely number1+1000.
(Your frequency array solution does exactly this while also making use of the fact that the bounds on numbers are relatively small.)
TL;DR avoid string-based concatenation of numbers