### Naim_Hasan's blog

By Naim_Hasan, history, 6 months ago, ,

Update: Solved. Special thanks to mello

Hello,

I was solving this https://codeforces.com/contest/1/problem/B

I have write one function to convert an Alphabet number into decimal number.

For example BC turns into 55. Similarly RZ becomes 494.

Here is my implementation https://ideone.com/2J0hCq

But i am facing problem to do the reverse.

For 55, my code shows BC which is right but for 494 it shows S@ which is wrong.

Here is my implementation https://ideone.com/OuUJD3

I found that the problem is causing when input is a multiple of 26.

Help needed.

• -14

 » 6 months ago, # |   0 If y == 0, that’s when you get the @ sign. Instead, if y == 0, put a Z there because A-Y is 1-25, so Z is the only one left to be 0. Then your code will look like this: string F(int n){ string Ans; while(n){ int y = n%26; if (y == 0){ Ans += ‘Z’; }else{ Ans += (char)(y+'A'-1); } n /= 26; } reverse(Ans.begin(),Ans.end()); return Ans; } This doesn’t work for multiples of 26 though. For 26 it outputs AZ and for 52 it outputs BZ. This is because the Z at the end counts as 1 extra 26. You see for AZ and BZ, they would be correct if they were Z and AZ. To correct this, after n /= 26, do n-- only if you just put a Z. Then, the code will look like this: string F(int n){ string Ans; while(n){ int y = n%26; if (y == 0){ Ans += ‘Z’; n /= 26; n--; }else{ Ans += (char)(y+'A'-1); n /= 26; } } reverse(Ans.begin(),Ans.end()); return Ans; } 
•  » » 6 months ago, # ^ |   0 Thanks for your time. Your idea worked perfectly.
 » 6 months ago, # |   0 Auto comment: topic has been updated by Naim_Hasan (previous revision, new revision, compare).
 » 6 months ago, # |   0 Auto comment: topic has been updated by Naim_Hasan (previous revision, new revision, compare).