title: Lexicographically Next String
signature: function lexicographicallyNextString($s) {
test_code: <?php
  
  
  // SOLUTION CODE 
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  function validateSolution($actual, $expected){
      return serialize($actual) == serialize($expected);
  }
  
  function driver($s, $expected){
      try{
        if (validateSolution(PLACEHOLDER_FN_NAME($s), $expected)){
          return "PASSED";
        }
        return "FAILED";
      }
      catch (Exception $exception_obj) {
        return get_class($exception_obj);
      }
  }
  
  function main(){
      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"));
      
  }
  
  main();
  ?>
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;
  }