First Letter to Appear Twice

[kevin]

First Letter to Appear Twice

Given a string s consisting of lowercase English letters, return the first letter to appear twice.

Note:

    A letter a appears twice before another letter b if the second occurrence of a is before the second occurrence of b.
    s will contain at least one letter that appears twice.


    Solution #1

PlayBASIC Code: [Select]

    /*
    
2351. First Letter to Appear Twice

Given a string s consisting of lowercase English letters, return the first letter to appear twice.

Note:

    A letter a appears twice before another letter b if the second occurrence of a is before the second occurrence of b.
    s will contain at least one letter that appears twice.
    
    */


    print repeatedCharacter("abccbaacz")
    print repeatedCharacter("abcdd")

    Sync
    waitkey


function repeatedCharacter(s$)
    
    Dim ChrMap(26)
    for lp =1 to len(s$)
            ThisCHR=mid(s$,lp)        
            if ThisChr>=asc("a") and ThisChr<=asc("z")
                Index    =ThisChr-asc("a")            
                if ChrMap(Index)
                    exitfunction chr$(ThisCHR)                
                endif
                ChrMap(Index)++
            endif
    next

EndFunction Result$

    Solution #2

PlayBASIC Code: [Select]

   /*
   
2351. First Letter to Appear Twice

Given a string s consisting of lowercase English letters, return the first letter to appear twice.

Note:

    A letter a appears twice before another letter b if the second occurrence of a is before the second occurrence of b.
    s will contain at least one letter that appears twice.
   
   */


   print repeatedCharacter("abccbaacz")
   print repeatedCharacter("abcdd")

   Sync
   waitkey


function repeatedCharacter(s$)
   
   BitMap =   0
   for lp =1 to len(s$)
         ThisCHR=mid(s$,lp)      
         if ThisChr>=asc("a") and ThisChr<=asc("z")
            ThisBIT      =1<< (ThisChr-asc("a"))         
            if BitMap & ThisBIT
               exitfunction chr$(ThisCHR)            
            endif
            BitMap |= ThisBIT
         endif
   next

EndFunction Result$