Et tall kalles lykkelig hvis det fører til 1 etter en sekvens av trinn der hvert trinntall erstattes av summen av kvadrater av sifferet, det vil si at hvis vi starter med Happy Number og fortsetter å erstatte det med siffer kvadratsum, når vi 1. 

Eksempler:  

 Input: n = 19   
 Output: True   
 19 is Happy Number   
 1^2 + 9^2 = 82   
 8^2 + 2^2 = 68   
 6^2 + 8^2 = 100   
 1^2 + 0^2 + 0^2 = 1   
 As we reached to 1 19 is a Happy Number.   
  
 Input: n = 20   
 Output: False  
 Et tall vil ikke være et lykkelig tall når det lager en løkke i sekvensen, det vil si at det berører et tall i sekvens som allerede er trykket. Så for å sjekke om et tall er fornøyd eller ikke, kan vi beholde et sett hvis det samme tallet oppstår igjen, flagger vi resultatet som ikke fornøyd. En enkel funksjon på tilnærmingen ovenfor kan skrives som nedenfor -    
 C++   
   // method return true if n is Happy Number   int     numSquareSum  (  int     n  )     {      int     num     =     0  ;      while     (  n     !=     0  )     {      int     digit     =     n     %     10  ;      num     +=     digit     *     digit  ;      n     /=     10  ;      }      return     num  ;   }   int     isHappyNumber  (  int     n  )   {      set   <  int  >     st  ;      while     (  1  )      {      n     =     numSquareSum  (  n  );      if     (  n     ==     1  )      return     true  ;      if     (  st  .  find  (  n  )     !=     st  .  end  ())      return     false  ;      st  .  insert  (  n  );      }   }   
  Java   
   // method return true if n is Happy Number   public     static     int     numSquareSum  (  int     n  )   {      int     num     =     0  ;      while     (  n     !=     0  )     {      int     digit     =     n     %     10  ;      num     +=     digit     *     digit  ;      n     /=     10  ;      }      return     num  ;   }   static     boolean     isHappyNumber  (  int     n  )   {      HashSet   <  Integer  >     st     =     new     HashSet   <>  ();      while     (  true  )     {      n     =     numSquareSum  (  n  );      if     (  n     ==     1  )      return     true  ;      if     (  st  .  contains  (  n  ))      return     false  ;      st  .  add  (  n  );      }   }   // This code is contributed by Princi Singh   
  Python   
   # method return true if n is Happy Number   def   numSquareSum  (  n  ):   num   =   0   while  (  n  ):   digit   =   n   %   10   num   =   num   +   digit  *  digit   n   =   n   //   10   return   num   def   isHappyNumber  (  n  ):   st   =   set  ()   while   (  1  ):   n   =   numSquareSum  (  n  )   if   (  n   ==   1  ):   return   True   if   n   not   in   st  :   return   False   st  .  insert  (  n  )   
  C#   
   // Method return true if n is Happy Number   static     int     numSquareSum  (  int     n  )   {      int     num     =     0  ;      while     (  n     !=     0  )     {      int     digit     =     n     %     10  ;      num     +=     digit     *     digit  ;      n     /=     10  ;      }      return     num  ;   }   static     int     isHappyNumber  (  int     n  )   {      HashSet   <  int  >     st     =     new     HashSet   <>  ();      while     (  1  )     {      n     =     numSquareSum  (  n  );      if     (  n     ==     1  )      return     true  ;      if     (  st  .  Contains  (  n  ))      return     false  ;      st  .  Add  (  n  );      }   }   // This code is contributed by 29AjayKumar   
  JavaScript   
    <  script  >   // method return true if n is Happy Number      function     numSquareSum  (  n  )     {      let     num     =     0  ;      while     (  n     !==     0  )     {      let     digit     =     n     %     10  ;      num     +=     digit     *     digit  ;      n     =     Math  .  floor  (  n     /     10  );      }      return     num  ;      }      let     st     =     new     Set  ();      while     (  1  )      {      n     =     numSquareSum  (  n  );      if     (  n     ==     1  )      return     true  ;      if     (  st  .  has  (  n  ))      return     false  ;      st  .  add  (  n  );      }   }   //This code is contributed by Mayank Tyagi    <  /script>   
   
    Kompleksitetsanalyse:    
 
    Tidskompleksitet:    O(n*log(n)).    
    Hjelpeplass:    O(n) siden bruk av ekstra sett for lagring  
 
 Vi kan løse dette problemet uten å bruke ekstra plass, og den teknikken kan også brukes i noen andre lignende problemer. Hvis vi behandler hvert tall som en node og erstatning med kvadratsumsiffer som en kobling, er dette problemet det samme som    finne en løkke i en lenkeliste    :   
 
 Så som en foreslått løsning fra lenken ovenfor vil vi holde to tall sakte og raske, begge initialisere fra et gitt nummer sakte erstattes ett trinn om gangen og raskt erstattes to trinn om gangen. Hvis de møtes på 1 så er det gitte nummeret Happy Number ellers ikke.    
 C++   
   // C++ program to check a number is a Happy number or not   #include          using     namespace     std  ;   // Utility method to return sum of square of digit of n   int     numSquareSum  (  int     n  )   {      int     squareSum     =     0  ;      while     (  n  )     {      squareSum     +=     (  n     %     10  )     *     (  n     %     10  );      n     /=     10  ;      }      return     squareSum  ;   }   // method return true if n is Happy number   bool     isHappynumber  (  int     n  )   {      int     slow       fast  ;      // initialize slow and fast by n      slow     =     fast     =     n  ;      do     {      // move slow number by one iteration      slow     =     numSquareSum  (  slow  );      // move fast number by two iteration      fast     =     numSquareSum  (  numSquareSum  (  fast  ));      }     while     (  slow     !=     fast  );      // if both number meet at 1 then return true      return     (  slow     ==     1  );   }   // Driver code to test above methods   int     main  ()   {      int     n     =     13  ;      if     (  isHappynumber  (  n  ))      cout      < <     n      < <     ' is a Happy number  n  '  ;      else      cout      < <     n      < <     ' is not a Happy number  n  '  ;   }   // This code is contributed by divyeshrabadiya07   
  C   
   // C program to check a number is a Happy number or not   #include         #include         // Utility method to return sum of square of digit of n   int     numSquareSum  (  int     n  )   {      int     squareSum     =     0  ;      while     (  n  )     {      squareSum     +=     (  n     %     10  )     *     (  n     %     10  );      n     /=     10  ;      }      return     squareSum  ;   }   // method return true if n is Happy number   bool     isHappynumber  (  int     n  )   {      int     slow       fast  ;      // initialize slow and fast by n      slow     =     fast     =     n  ;      do     {      // move slow number by one iteration      slow     =     numSquareSum  (  slow  );      // move fast number by two iteration      fast     =     numSquareSum  (  numSquareSum  (  fast  ));      }     while     (  slow     !=     fast  );      // if both number meet at 1 then return true      return     (  slow     ==     1  );   }   // Driver code to test above methods   int     main  ()   {      int     n     =     13  ;      if     (  isHappynumber  (  n  ))      printf  (  '%d is a Happy number  n  '       n  );      else      printf  (  '%d is not a Happy number  n  '       n  );   }   // This code is contributed by Sania Kumari Gupta   // (kriSania804)   
  Java   
   // Java program to check a number is a Happy   // number or not   class   GFG     {       // Utility method to return sum of square of   // digit of n   static     int     numSquareSum  (  int     n  )   {      int     squareSum     =     0  ;      while     (  n  !=     0  )      {      squareSum     +=     (  n     %     10  )     *     (  n     %     10  );      n     /=     10  ;      }      return     squareSum  ;   }       // method return true if n is Happy number   static     boolean     isHappynumber  (  int     n  )   {      int     slow       fast  ;          // initialize slow and fast by n      slow     =     fast     =     n  ;      do      {      // move slow number      // by one iteration      slow     =     numSquareSum  (  slow  );          // move fast number      // by two iteration      fast     =     numSquareSum  (  numSquareSum  (  fast  ));          }      while     (  slow     !=     fast  );          // if both number meet at 1      // then return true      return     (  slow     ==     1  );   }       // Driver code to test above methods   public     static     void     main  (  String  []     args  )   {      int     n     =     13  ;      if     (  isHappynumber  (  n  ))      System  .  out  .  println  (  n     +         ' is a Happy number'  );      else      System  .  out  .  println  (  n     +         ' is not a Happy number'  );   }   }   
  Python   
   # Python3 program to check if a number is a Happy number or not   # Utility method to return the sum of squares of digits of n   def   num_square_sum  (  n  ):   square_sum   =   0   while   n  :   square_sum   +=   (  n   %   10  )   **   2   n   //=   10   return   square_sum   # Method returns True if n is a Happy number   def   is_happy_number  (  n  ):   # Initialize slow and fast pointers   slow   =   n   fast   =   n   while   True  :   # Move slow pointer by one iteration   slow   =   num_square_sum  (  slow  )   # Move fast pointer by two iterations   fast   =   num_square_sum  (  num_square_sum  (  fast  ))   if   slow   !=   fast  :   continue   else  :   break   # If both pointers meet at 1 then return True   return   slow   ==   1   # Driver Code   n   =   13   if   is_happy_number  (  n  ):   print  (  n     'is a Happy number'  )   else  :   print  (  n     'is not a Happy number'  )   
  C#   
   // C# program to check a number   // is a Happy number or not   using     System  ;   class     GFG     {   // Utility method to return    // sum of square of digit of n   static     int     numSquareSum  (  int     n  )   {      int     squareSum     =     0  ;      while     (  n  !=     0  )      {      squareSum     +=     (  n     %     10  )     *         (  n     %     10  );      n     /=     10  ;      }      return     squareSum  ;   }   // method return true if   // n is Happy number   static     bool     isHappynumber  (  int     n  )   {      int     slow       fast  ;      // initialize slow and      // fast by n      slow     =     fast     =     n  ;      do      {          // move slow number      // by one iteration      slow     =     numSquareSum  (  slow  );      // move fast number      // by two iteration      fast     =     numSquareSum  (  numSquareSum  (  fast  ));      }      while     (  slow     !=     fast  );      // if both number meet at 1      // then return true      return     (  slow     ==     1  );   }   // Driver code   public     static     void     Main  ()   {      int     n     =     13  ;      if     (  isHappynumber  (  n  ))      Console  .  WriteLine  (  n     +         ' is a Happy number'  );      else      Console  .  WriteLine  (  n     +         ' is not a Happy number'  );   }   }   // This code is contributed by anuj_67.   
  JavaScript   
    <  script  >   // Javascript program to check a number is a Happy   // number or not   // Utility method to return sum of square of   // digit of n   function     numSquareSum  (  n  )   {      var     squareSum     =     0  ;      while     (  n  !=     0  )      {      squareSum     +=     (  n     %     10  )     *     (  n     %     10  );      n     =     parseInt  (  n  /  10  );      }      return     squareSum  ;   }       // method return true if n is Happy number   function     isHappynumber  (  n  )   {      var     slow       fast  ;          // initialize slow and fast by n      slow     =     fast     =     n  ;      do      {      // move slow number      // by one iteration      slow     =     numSquareSum  (  slow  );          // move fast number      // by two iteration      fast     =     numSquareSum  (  numSquareSum  (  fast  ));          }      while     (  slow     !=     fast  );          // if both number meet at 1      // then return true      return     (  slow     ==     1  );   }       // Driver code to test above methods   var     n     =     13  ;   if     (  isHappynumber  (  n  ))      document  .  write  (  n     +         ' is a Happy number'  );   else      document  .  write  (  n     +         ' is not a Happy number'  );       // This code contributed by Princi Singh     <  /script>   
  PHP   
      // PHP program to check a number   // is a Happy number or not   // Utility method to return    // sum of square of digit of n   function   numSquareSum  (   $n  )   {   $squareSum   =   0  ;   while   (  $n  )   {   $squareSum   +=   (  $n   %   10  )   *   (  $n   %   10  );   $n   /=   10  ;   }   return   $squareSum  ;   }   // method return true if   // n is Happy number   function   isHappynumber  (   $n  )   {   $slow  ;   $fast  ;   // initialize slow    // and fast by n   $slow   =   $n  ;   $fast   =   $n  ;   do   {   // move slow number   // by one iteration   $slow   =   numSquareSum  (  $slow  );   // move fast number   // by two iteration   $fast   =   numSquareSum  (  numSquareSum  (  $fast  ));   }   while   (  $slow   !=   $fast  );   // if both number meet at 1    // then return true   return   (  $slow   ==   1  );   }   // Driver Code   $n   =   13  ;   if   (  isHappynumber  (  $n  ))   echo   $n      ' is a Happy number  n  '  ;   else   echo   n      ' is not a Happy number  n  '  ;   // This code is contributed by anuj_67.   ?>   
   
    Utgang:       
 
 13 is a Happy Number  
    Kompleksitetsanalyse:    
 
    Tidskompleksitet:    O(n*log(n)).   
    Hjelpeplass:    O(1).   
 
  
    En annen tilnærming for å løse dette problemet uten ekstra plass.     
 Et tall kan ikke være et lykkelig tall     hvis summen av kvadratet av sifrene som er oppnådd er et ensifret tall bortsett fra 1 eller 7    . Dette er fordi 1 og 7 er de eneste ensifrede lykkelige tallene. Ved å bruke denne informasjonen kan vi utvikle en tilnærming som vist i koden nedenfor -   
 C++   
   // C++ program to check if a number is a Happy number or   // not.   #include          using     namespace     std  ;   // Method - returns true if the input is a happy number else   // returns false   bool     isHappynumber  (  int     n  )   {      int     sum     =     n       x     =     n  ;      // This loop executes till the sum of square of digits      // obtained is not a single digit number      while     (  sum     >     9  )     {      sum     =     0  ;      // This loop finds the sum of square of digits      while     (  x     >     0  )     {      int     d     =     x     %     10  ;      sum     +=     d     *     d  ;      x     /=     10  ;      }      x     =     sum  ;      }      if     (  sum     ==     7     ||     sum     ==     1  )      return     true  ;      return     false  ;   }   int     main  ()   {      int     n     =     13  ;      if     (  isHappynumber  (  n  ))      cout      < <     n      < <     ' is a Happy number'  ;      else      cout      < <     n      < <     ' is not a Happy number'  ;      return     0  ;   }   // This code is contributed by Sania Kumari Gupta   
  C   
   // C program to check if a number is a Happy number or   // not.   #include         #include         // Method - returns true if the input is a happy number else   // returns false   bool     isHappynumber  (  int     n  )   {      int     sum     =     n       x     =     n  ;      // This loop executes till the sum of square of digits      // obtained is not a single digit number      while     (  sum     >     9  )     {      sum     =     0  ;      // This loop finds the sum of square of digits      while     (  x     >     0  )     {      int     d     =     x     %     10  ;      sum     +=     d     *     d  ;      x     /=     10  ;      }      x     =     sum  ;      }      if     (  sum     ==     7     ||     sum     ==     1  )      return     true  ;      return     false  ;   }   int     main  ()   {      int     n     =     13  ;      if     (  isHappynumber  (  n  ))      printf  (  '%d is a Happy number'       n  );      else      printf  (  '%d is not a Happy number'       n  );      return     0  ;   }   // This code is contributed by Sania Kumari Gupta   
  Java   
   // This code is contributed by Vansh Sodhi.   // Java program to check if a number is a Happy number or   // not.   class   GFG     {      // method - returns true if the input is a happy      // number else returns false      static     boolean     isHappynumber  (  int     n  )      {      int     sum     =     n       x     =     n  ;      // this loop executes till the sum of square of      // digits obtained is not a single digit number      while     (  sum     >     9  )     {      sum     =     0  ;      // this loop finds the sum of square of digits      while     (  x     >     0  )     {      int     d     =     x     %     10  ;      sum     +=     d     *     d  ;      x     /=     10  ;      }      x     =     sum  ;      }      if     (  sum     ==     1     ||     sum     ==     7  )      return     true  ;      return     false  ;      }      // Driver code      public     static     void     main  (  String  []     args  )      {      int     n     =     13  ;      if     (  isHappynumber  (  n  ))      System  .  out  .  println  (  n     +     ' is a Happy number'  );      else      System  .  out  .  println  (  n      +     ' is not a Happy number'  );      }   }   
  Python   
   # Python3 program to check if a number is a Happy number or not.   # Method - returns true if the input is   # a happy number else returns false   def   isHappynumber  (  n  ):   Sum     x   =   n     n   # This loop executes till the sum   # of square of digits obtained is   # not a single digit number   while   Sum   >   9  :   Sum   =   0   # This loop finds the sum of   # square of digits   while   x   >   0  :   d   =   x   %   10   Sum   +=   d   *   d   x   =   int  (  x   /   10  )   x   =   Sum   if   Sum   ==   1   or   Sum   ==   7  :   return   True   return   False   n   =   13   if   isHappynumber  (  n  ):   print  (  n     'is a Happy number'  )   else  :   print  (  n     'is not a Happy number'  )   # This code is contributed by mukesh07.   
  C#   
   // C# program to check if a number   // is a Happy number or not.   using     System  ;   class     GFG     {      // Method - returns true if the input is      // a happy number else returns false      static     bool     isHappynumber  (  int     n  )      {      int     sum     =     n       x     =     n  ;      // This loop executes till the sum      // of square of digits obtained is      // not a single digit number      while     (  sum     >     9  )     {      sum     =     0  ;      // This loop finds the sum of      // square of digits      while     (  x     >     0  )     {      int     d     =     x     %     10  ;      sum     +=     d     *     d  ;      x     /=     10  ;      }      x     =     sum  ;      }      if     (  sum     ==     1     ||     sum     ==     7  )      return     true  ;      return     false  ;      }      // Driver code      public     static     void     Main  (  String  []     args  )      {      int     n     =     13  ;      if     (  isHappynumber  (  n  ))      Console  .  WriteLine  (  n     +     ' is a Happy number'  );      else      Console  .  WriteLine  (  n     +     ' is not a Happy number'  );      }   }   // This code is contributed by 29AjayKumar   
  JavaScript   
    <  script  >   // This code is contributed by Vansh Sodhi.   // javascript program to check if a number is a Happy number or not.      // method - returns true if the input is a happy      // number else returns false      function     isHappynumber  (  n  )      {      var     sum     =     n       x     =     n  ;      // this loop executes till the sum of square of      // digits obtained is not a single digit number      while  (  sum     >     9  )         {      sum     =     0  ;      // this loop finds the sum of square of digits      while     (  x     >     0  )         {      var     d     =     x     %     10  ;      sum     +=     d     *     d  ;      x     /=     10  ;      }      x     =     sum  ;      }      if  (  sum     ==     1     ||     sum     ==     7  )      return     true  ;      return     false  ;   }   // Driver code      var     n     =     13  ;      if     (  isHappynumber  (  n  ))      document  .  write  (  n     +         ' is a Happy number'  );      else      document  .  write  (  n     +         ' is not a Happy number'  );       // This code is contributed by 29AjayKumar     <  /script>   
    
  Produksjon   
13 is a Happy number 
 
    Kompleksitetsanalyse:    
 
    Tidskompleksitet:    O(n*log(n)).   
    Hjelpeplass:    O(1).   
 
 Se artikkelen din som vises på GeeksforGeeks hovedside og hjelp andre nerder.   
    
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