title: Lexicographically Next String
signature: lexicographicallyNextString :: String -> String
  lexicographicallyNextString s = 
test_code: import Text.Printf
  import Control.Exception (catch, SomeException)
  import Data.Typeable
  import qualified Data.List as List
  import qualified Data.Map as Map
  import qualified Data.Set as Set
  
  -- SOLUTION CODE
  -- ============================================
  
  PLACEHOLDER_CODE_BODY
  
  -- TESTING CODE 
  -- ============================================
  validateSolution :: String -> String -> Bool
  validateSolution actual expected = do
      actual == expected
  
  
  driver :: String -> String -> String
  driver s expected = do
      if (validateSolution (PLACEHOLDER_FN_NAME s) expected)
          then "PASSED"
      else "FAILED"
  
  main = do
      printf "TEST-0...%s\n" (driver ("amKIRzPiqLTIy") ("amKIRzPiqLTIz") )
  
      printf "TEST-1...%s\n" (driver ("68") ("69") )
  
      printf "TEST-2...%s\n" (driver ("100") ("110") )
  
      printf "TEST-3...%s\n" (driver ("f") ("g") )
  
      printf "TEST-4...%s\n" (driver ("802205375") ("802206375") )
  
      printf "TEST-5...%s\n" (driver ("0111") ("0211") )
  
      printf "TEST-6...%s\n" (driver ("GRjRYIvYwgua") ("GRjRYIvYwgub") )
  
      printf "TEST-7...%s\n" (driver ("8139910006809") ("813:910006809") )
  
      printf "TEST-8...%s\n" (driver ("100101") ("200101") )
  
      printf "TEST-9...%s\n" (driver ("rw") ("rx") )
  
source_py: def lexicographically_next_string(s):
      if (s == ' '):
          return 'a'
      i = (len(s) - 1)
      while ((s[i] == 'z') and (i >= 0)):
          i -= 1
      if (i == (- 1)):
          s = (s + 'a')
      else:
          s = s.replace(s[i], chr((ord(s[i]) + 1)), 1)
      return s
source_cpp: string lexicographically_next_string(string s) {
    if ( s == "" ) return "a";
    int i = s . length ( ) - 1;
    while ( s [ i ] == 'z' && i >= 0 ) i --;
    if ( i == - 1 ) s = s + 'a';
    else s [ i ] ++;
    return s;
  }