Wahrscheinlichkeit, dass Springer auf dem Schachbrett bleibt

Wahrscheinlichkeit, dass Springer auf dem Schachbrett bleibt
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Gegeben a n*n Schachbrett und die Ritter Position (x y) Jedes Mal, wenn der Springer ziehen soll, wählt er einheitlich einen von acht möglichen Zügen zufällig (auch wenn die Figur vom Schachbrett verschwinden würde) und bewegt sich Dort. Der Ritter geht weiter bewegen, bis es genau gemacht hat k bewegt oder hat zog los das Schachbrett. Die Aufgabe besteht darin finden Die Wahrscheinlichkeit dass der Ritter Überreste auf der Planke nachdem es das getan hat gestoppt bewegen.

Notiz: Ein Schachspringer kann acht mögliche Züge machen. Jede Bewegung besteht aus zwei Zellen in einer Himmelsrichtung und dann einer Zelle in einer orthogonalen Richtung.

Beispiele:  

Eingang: n = 8 x = 0 y = 0 k = 1
Ausgabe: 0,25
Erläuterung: Der Springer beginnt bei (0 0) und liegt nach einem Schritt nur auf 2 von 8 Positionen innerhalb des Bretts, nämlich (1 2) und (2 1). Somit beträgt die Wahrscheinlichkeit 2/8 = 0,25.

Eingabe: n = 8 x = 0 y = 0 k = 3
Ausgabe: 0,125

Eingang: n = 4 x = 1 y = 2 k = 4
Ausgabe: 0,024414

Inhaltsverzeichnis

Verwendung von Top-Down-Dp (Memoisierung) – O(n*n*k) Zeit und O(n*n*k) Raum

Die Wahrscheinlichkeit, dass der Springer nach k Zügen auf dem Schachbrett bleibt, ist gleich der durchschnittlichen Wahrscheinlichkeit, dass der Springer nach k - 1 Zügen an den vorherigen acht Positionen verbleibt. Ebenso hängt die Wahrscheinlichkeit nach k-1 Zügen vom Durchschnitt der Wahrscheinlichkeit nach k-2 Zügen ab. Die Idee ist zu verwenden Auswendiglernen um die Wahrscheinlichkeiten früherer Züge zu speichern und ihren Durchschnitt zu ermitteln, um das Endergebnis zu berechnen.
Erstellen Sie dazu eine 3D-Array-Memo[][][] Wo Memo[i][j][k] speichert die Wahrscheinlichkeit, dass sich der Springer nach k Zügen in der Zelle (i j) befindet. Wenn k Null ist, ist der Anfangszustand erreicht Rückkehr 1 Andernfalls untersuchen Sie die vorherigen acht Positionen und ermitteln Sie den Durchschnitt ihrer Wahrscheinlichkeiten.

C++
   // C++ program to find the probability of the   // knight to remain inside the chessboard   #include          using     namespace     std  ;   // recursive function to calculate   // knight probability   double     knightProbability  (  int     n       int     x       int     y       int     k           vector   <  vector   <  vector   <  double  >>>     &  memo  ){      // Base case initial probability      if  (  k     ==     0  )     return     1.0  ;      // check if already calculated      if  (  memo  [  x  ][  y  ][  k  ]     !=     -1  )     return     memo  [  x  ][  y  ][  k  ];      vector   <  vector   <  int  >>     directions     =     {{  1       2  }     {  2       1  }     {  2       -1  }      {  1       -2  }     {  -1       -2  }     {  -2       -1  }     {  -2       1  }     {  -1       2  }};      memo  [  x  ][  y  ][  k  ]     =     0  ;      double     cur     =     0.0  ;      // for every position reachable from (xy)      for  (  auto     d  :  directions  ){      int     u     =     x     +     d  [  0  ];      int     v     =     y     +     d  [  1  ];      // if this position lie inside the board      if     (  u     >=     0     &&     u      <     n     &&     v     >=     0     &&     v      <     n  )      cur     +=     knightProbability  (  n       u       v       k  -1       memo  )     /     8.0  ;      }      return     memo  [  x  ][  y  ][  k  ]     =     cur  ;   }   // Function to find the probability   double     findProb  (  int     n       int     x       int     y       int     k  )     {      // Initialize memo to store results      vector   <  vector   <  vector   <  double  >>>     memo  (  n           vector   <  vector   <  double  >>  (  n        vector   <  double  >     (  k  +  1       -1  )));      return     knightProbability  (  n       x       y       k       memo  );   }   int     main  (){      int     n     =     8       x     =     0       y     =     0       k     =     3  ;      cout      < <     findProb  (  n       x       y       k  )      < <     endl  ;      return     0  ;   }   
Java
   // Java program to find the probability of the   // knight to remain inside the chessboard   class   GfG     {      // recursive function to calculate      // knight probability      static     double     knightProbability  (  int     n       int     x           int     y       int     k       double  [][][]     memo  )     {      // Base case initial probability      if     (  k     ==     0  )     return     1.0  ;      // check if already calculated      if     (  memo  [  x  ][  y  ][  k  ]     !=     -  1  )     return     memo  [  x  ][  y  ][  k  ]  ;      int  [][]     directions     =     {{  1       2  }     {  2       1  }     {  2       -  1  }     {  1       -  2  }      {  -  1       -  2  }     {  -  2       -  1  }     {  -  2       1  }     {  -  1       2  }};      memo  [  x  ][  y  ][  k  ]     =     0  ;      double     cur     =     0.0  ;      // for every position reachable from (x y)      for     (  int  []     d     :     directions  )     {      int     u     =     x     +     d  [  0  ]  ;      int     v     =     y     +     d  [  1  ]  ;      // if this position lies inside the board      if     (  u     >=     0     &&     u      <     n     &&     v     >=     0     &&     v      <     n  )      cur     +=     knightProbability  (  n       u       v       k     -     1       memo  )     /     8.0  ;      }      return     memo  [  x  ][  y  ][  k  ]     =     cur  ;      }      // Function to find the probability      static     double     findProb  (  int     n       int     x       int     y       int     k  )     {      // Initialize memo to store results      double  [][][]     memo     =     new     double  [  n  ][  n  ][  k     +     1  ]  ;      for     (  int     i     =     0  ;     i      <     n  ;     i  ++  )     {      for     (  int     j     =     0  ;     j      <     n  ;     j  ++  )     {      for     (  int     m     =     0  ;     m      <=     k  ;     m  ++  )     {      memo  [  i  ][  j  ][  m  ]     =     -  1  ;      }      }      }      return     knightProbability  (  n       x       y       k       memo  );      }      public     static     void     main  (  String  []     args  )     {      int     n     =     8       x     =     0       y     =     0       k     =     3  ;      System  .  out  .  println  (  findProb  (  n       x       y       k  ));      }   }   
Python
   # Python program to find the probability of the   # knight to remain inside the chessboard   # recursive function to calculate   # knight probability   def   knightProbability  (  n     x     y     k     memo  ):   # Base case initial probability   if   k   ==   0  :   return   1.0   # check if already calculated   if   memo  [  x  ][  y  ][  k  ]   !=   -  1  :   return   memo  [  x  ][  y  ][  k  ]   directions   =   [   [  1     2  ]   [  2     1  ]   [  2     -  1  ]   [  1     -  2  ]   [  -  1     -  2  ]   [  -  2     -  1  ]   [  -  2     1  ]   [  -  1     2  ]   ]   memo  [  x  ][  y  ][  k  ]   =   0   cur   =   0.0   # for every position reachable from (x y)   for   d   in   directions  :   u   =   x   +   d  [  0  ]   v   =   y   +   d  [  1  ]   # if this position lies inside the board   if   0    <=   u    <   n   and   0    <=   v    <   n  :   cur   +=   knightProbability  (  n     u     v     k   -   1     memo  )   /   8.0   memo  [  x  ][  y  ][  k  ]   =   cur   return   cur   # Function to find the probability   def   findProb  (  n     x     y     k  ):   # Initialize memo to store results   memo   =   [[[  -  1   for   _   in   range  (  k   +   1  )]   for   _   in   range  (  n  )]   for   _   in   range  (  n  )]   return   knightProbability  (  n     x     y     k     memo  )   n     x     y     k   =   8     0     0     3   print  (  findProb  (  n     x     y     k  ))   
C#
   // C# program to find the probability of the   // knight to remain inside the chessboard   using     System  ;   class     GfG     {      // recursive function to calculate      // knight probability      static     double     KnightProbability  (  int     n       int     x           int     y       int     k       double  []     memo  )     {      // Base case initial probability      if     (  k     ==     0  )     return     1.0  ;      // check if already calculated      if     (  memo  [  x       y       k  ]     !=     -  1  )     return     memo  [  x       y       k  ];      int  []     directions     =     {{  1       2  }     {  2       1  }     {  2       -  1  }     {  1       -  2  }      {  -  1       -  2  }     {  -  2       -  1  }     {  -  2       1  }     {  -  1       2  }};      memo  [  x       y       k  ]     =     0  ;      double     cur     =     0.0  ;      // for every position reachable from (x y)      for     (  int     i     =     0  ;     i      <     8  ;     i  ++  )     {      int     u     =     x     +     directions  [  i       0  ];      int     v     =     y     +     directions  [  i       1  ];      // if this position lies inside the board      if     (  u     >=     0     &&     u      <     n     &&     v     >=     0     &&     v      <     n  )     {      cur     +=     KnightProbability  (  n       u       v       k     -     1       memo  )     /     8.0  ;      }      }      return     memo  [  x       y       k  ]     =     cur  ;      }      // Function to find the probability      static     double     FindProb  (  int     n       int     x       int     y       int     k  )     {      // Initialize memo to store results      double  []     memo     =     new     double  [  n       n       k     +     1  ];      for     (  int     i     =     0  ;     i      <     n  ;     i  ++  )     {      for     (  int     j     =     0  ;     j      <     n  ;     j  ++  )     {      for     (  int     m     =     0  ;     m      <=     k  ;     m  ++  )     {      memo  [  i       j       m  ]     =     -  1  ;      }      }      }      return     KnightProbability  (  n       x       y       k       memo  );      }      static     void     Main  ()     {      int     n     =     8       x     =     0       y     =     0       k     =     3  ;      Console  .  WriteLine  (  FindProb  (  n       x       y       k  ));      }   }   
JavaScript
   // JavaScript program to find the probability of the   // knight to remain inside the chessboard   // recursive function to calculate   // knight probability   function     knightProbability  (  n       x       y       k       memo  )     {      // Base case initial probability      if     (  k     ===     0  )     return     1.0  ;      // check if already calculated      if     (  memo  [  x  ][  y  ][  k  ]     !==     -  1  )     return     memo  [  x  ][  y  ][  k  ];      const     directions     =     [      [  1       2  ]     [  2       1  ]     [  2       -  1  ]     [  1       -  2  ]      [  -  1       -  2  ]     [  -  2       -  1  ]     [  -  2       1  ]     [  -  1       2  ]      ];      memo  [  x  ][  y  ][  k  ]     =     0  ;      let     cur     =     0.0  ;      // for every position reachable from (x y)      for     (  let     d     of     directions  )     {      const     u     =     x     +     d  [  0  ];      const     v     =     y     +     d  [  1  ];      // if this position lies inside the board      if     (  u     >=     0     &&     u      <     n     &&     v     >=     0     &&     v      <     n  )     {      cur     +=     knightProbability  (  n       u       v       k     -     1       memo  )     /     8.0  ;      }      }      return     memo  [  x  ][  y  ][  k  ]     =     cur  ;   }   // Function to find the probability   function     findProb  (  n       x       y       k  )     {      // Initialize memo to store results      const     memo     =     Array  .  from  ({     length  :     n     }     ()     =>      Array  .  from  ({     length  :     n     }     ()     =>     Array  (  k     +     1  ).  fill  (  -  1  )));      return     knightProbability  (  n       x       y       k       memo  ).  toFixed  (  6  );   }   const     n     =     8       x     =     0       y     =     0       k     =     3  ;      console  .  log  (  findProb  (  n       x       y       k  ));   

Ausgabe
0.125  

Verwenden von Bottom-Up Dp (Tabulation) – O(n*n*k) Zeit und O(n*n*k) Raum

Der obige Ansatz kann mit optimiert werden von unten nach oben Tabellierung reduziert den zusätzlichen Platzbedarf für rekursive Stapel. Die Idee ist, eine 3 beizubehalten D-Array dp[][][] Wo dp[i][j][k] speichert die Wahrscheinlichkeit, dass der Ritter in der Zelle ist (i j) nach k bewegt sich. Initialisieren Sie die 0 Zustand von dp mit Wert 1 . Für jeden weiteren Zug die Wahrscheinlichkeit des Ritters wird sein gleich Zu Durchschnitt der Wahrscheinlichkeit von vorherige 8 Positionen danach k-1 bewegt sich.

C++
   // C++ program to find the probability of the   // knight to remain inside the chessboard   #include          using     namespace     std  ;   // Function to find the probability   double     findProb  (  int     n       int     x       int     y       int     k  )     {      // Initialize dp to store results of each step      vector   <  vector   <  vector   <  double  >>>     dp  (  n           vector   <  vector   <  double  >>  (  n        vector   <  double  >     (  k  +  1  )));          // Initialize dp for step 0      for     (  int     i     =     0  ;     i      <     n  ;     ++  i  )     {      for     (  int     j     =     0  ;     j      <     n  ;     ++  j  )     {      dp  [  i  ][  j  ][  0  ]     =     1.0  ;      }      }      vector   <  vector   <  int  >>     directions     =     {      {  1       2  }     {  2       1  }     {  2       -1  }     {  1       -2  }         {  -1       -2  }     {  -2       -1  }     {  -2       1  }     {  -1       2  }      };      for     (  int     move     =     1  ;     move      <=     k  ;     move  ++  )     {          // find probability for cell (i j)      for     (  int     i     =     0  ;     i      <     n  ;     ++  i  )     {      for     (  int     j     =     0  ;     j      <     n  ;     ++  j  )     {      double     cur     =     0.0  ;      // for every position reachable from (xy)      for     (  auto     d  :  directions  )     {      int     u     =     i     +     d  [  0  ];      int     v     =     j     +     d  [  1  ];      // if this position lie inside the board      if     (  u     >=     0     &&     u      <     n     &&     v     >=     0     &&     v      <     n  )      cur     +=     dp  [  u  ][  v  ][  move     -     1  ]     /     8.0  ;      }      // store the result      dp  [  i  ][  j  ][  move  ]     =     cur  ;      }      }      }      // return the result      return     dp  [  x  ][  y  ][  k  ];   }   int     main  (){      int     n     =     8       x     =     0       y     =     0       k     =     3  ;      cout      < <     findProb  (  n       x       y       k  )      < <     endl  ;      return     0  ;   }   
Java
   // Java program to find the probability of the   // knight to remain inside the chessboard   import     java.util.*  ;   class   GfG     {      // Function to find the probability      static     double     findProb  (  int     n       int     x       int     y       int     k  )     {      // Initialize dp to store results of each step      double  [][][]     dp     =     new     double  [  n  ][  n  ][  k     +     1  ]  ;      for     (  int     i     =     0  ;     i      <     n  ;     i  ++  )     {      for     (  int     j     =     0  ;     j      <     n  ;     j  ++  )     {      dp  [  i  ][  j  ][  0  ]     =     1  ;      }      }      int  [][]     directions     =     {      {  1       2  }     {  2       1  }     {  2       -  1  }     {  1       -  2  }         {  -  1       -  2  }     {  -  2       -  1  }     {  -  2       1  }     {  -  1       2  }      };      for     (  int     move     =     1  ;     move      <=     k  ;     move  ++  )     {      // find probability for cell (i j)      for     (  int     i     =     0  ;     i      <     n  ;     ++  i  )     {      for     (  int     j     =     0  ;     j      <     n  ;     ++  j  )     {      double     cur     =     0.0  ;      // for every position reachable from (x y)      for     (  int  []     d     :     directions  )     {      int     u     =     i     +     d  [  0  ]  ;      int     v     =     j     +     d  [  1  ]  ;      // if this position lies inside the board      if     (  u     >=     0     &&     u      <     n     &&     v     >=     0     &&     v      <     n  )     {      cur     +=     dp  [  u  ][  v  ][  move     -     1  ]     /     8.0  ;      }      }      // store the result      dp  [  i  ][  j  ][  move  ]     =     cur  ;      }      }      }      // return the result      return     dp  [  x  ][  y  ][  k  ]  ;      }      public     static     void     main  (  String  []     args  )     {      int     n     =     8       x     =     0       y     =     0       k     =     3  ;      System  .  out  .  println  (  findProb  (  n       x       y       k  ));      }   }   
Python
   # Python program to find the probability of the   # knight to remain inside the chessboard   # Function to find the probability   def   findProb  (  n     x     y     k  ):   # Initialize dp to store results of each step   dp   =   [[[  0   for   _   in   range  (  k   +   1  )]   for   _   in   range  (  n  )]   for   _   in   range  (  n  )]   for   i   in   range  (  n  ):   for   j   in   range  (  n  ):   dp  [  i  ][  j  ][  0  ]   =   1.0   directions   =   [[  1     2  ]   [  2     1  ]   [  2     -  1  ]   [  1     -  2  ]   [  -  1     -  2  ]   [  -  2     -  1  ]   [  -  2     1  ]   [  -  1     2  ]]   for   move   in   range  (  1     k   +   1  ):   # find probability for cell (i j)   for   i   in   range  (  n  ):   for   j   in   range  (  n  ):   cur   =   0.0   # for every position reachable from (x y)   for   d   in   directions  :   u   =   i   +   d  [  0  ]   v   =   j   +   d  [  1  ]   # if this position lies inside the board   if   0    <=   u    <   n   and   0    <=   v    <   n  :   cur   +=   dp  [  u  ][  v  ][  move   -   1  ]   /   8.0   # store the result   dp  [  i  ][  j  ][  move  ]   =   cur   # return the result   return   dp  [  x  ][  y  ][  k  ]   if   __name__   ==   '__main__'  :   n     x     y     k   =   8     0     0     3   print  (  findProb  (  n     x     y     k  ))   
C#
   // C# program to find the probability of the   // knight to remain inside the chessboard   using     System  ;   class     GfG     {      // Function to find the probability      static     double     findProb  (  int     n       int     x       int     y       int     k  )     {      // Initialize dp to store results of each step      double  []     dp     =     new     double  [  n       n       k     +     1  ];      for     (  int     i     =     0  ;     i      <     n  ;     i  ++  )     {      for     (  int     j     =     0  ;     j      <     n  ;     j  ++  )     {      dp  [  i       j       0  ]     =     1.0  ;      }      }      int  []     directions     =     {{  1       2  }     {  2       1  }     {  2       -  1  }     {  1       -  2  }         {  -  1       -  2  }     {  -  2       -  1  }     {  -  2       1  }     {  -  1       2  }};      for     (  int     move     =     1  ;     move      <=     k  ;     move  ++  )     {      // find probability for cell (i j)      for     (  int     i     =     0  ;     i      <     n  ;     ++  i  )     {      for     (  int     j     =     0  ;     j      <     n  ;     ++  j  )     {      double     cur     =     0.0  ;      // for every position reachable from (x y)      for     (  int     d     =     0  ;     d      <     directions  .  GetLength  (  0  );     d  ++  )     {      int     u     =     i     +     directions  [  d       0  ];      int     v     =     j     +     directions  [  d       1  ];      // if this position lies inside the board      if     (  u     >=     0     &&     u      <     n     &&     v     >=     0     &&     v      <     n  )     {      cur     +=     dp  [  u       v       move     -     1  ]     /     8.0  ;      }      }      // store the result      dp  [  i       j       move  ]     =     cur  ;      }      }      }      // return the result      return     dp  [  x       y       k  ];      }      static     void     Main  (  string  []     args  )     {      int     n     =     8       x     =     0       y     =     0       k     =     3  ;      Console  .  WriteLine  (  findProb  (  n       x       y       k  ));      }   }   
JavaScript
   // JavaScript program to find the probability of the   // knight to remain inside the chessboard   // Function to find the probability   function     findProb  (  n       x       y       k  )     {      // Initialize dp to store results of each step      let     dp     =     Array  .  from  ({     length  :     n     }     ()     =>         Array  .  from  ({     length  :     n     }     ()     =>     Array  (  k     +     1  ).  fill  (  0  ))      );      // Initialize dp for step 0      for     (  let     i     =     0  ;     i      <     n  ;     ++  i  )     {      for     (  let     j     =     0  ;     j      <     n  ;     ++  j  )     {      dp  [  i  ][  j  ][  0  ]     =     1.0  ;      }      }          let     directions     =     [[  1       2  ]     [  2       1  ]     [  2       -  1  ]     [  1       -  2  ]         [  -  1       -  2  ]     [  -  2       -  1  ]     [  -  2       1  ]     [  -  1       2  ]];      for     (  let     move     =     1  ;     move      <=     k  ;     move  ++  )     {          // find probability for cell (i j)      for     (  let     i     =     0  ;     i      <     n  ;     i  ++  )     {      for     (  let     j     =     0  ;     j      <     n  ;     j  ++  )     {      let     cur     =     0.0  ;      // for every position reachable from (x y)      for     (  let     d     of     directions  )     {      let     u     =     i     +     d  [  0  ];      let     v     =     j     +     d  [  1  ];      // if this position lies inside the board      if     (  u     >=     0     &&     u      <     n     &&     v     >=     0     &&     v      <     n  )     {      cur     +=     dp  [  u  ][  v  ][  move     -     1  ]     /     8.0  ;      }      }      // store the result      dp  [  i  ][  j  ][  move  ]     =     cur  ;      }      }      }      // return the result      return     dp  [  x  ][  y  ][  k  ].  toFixed  (  6  );   }   let     n     =     8       x     =     0       y     =     0       k     =     3  ;   console  .  log  (  findProb  (  n       x       y       k  ));   

Ausgabe
0.125  

Verwendung von raumoptimiertem Dp – O(n*n*k) Zeit und O(n*n) Raum

Der obige Ansatz erfordert nur vorherige Zustand der Wahrscheinlichkeiten zur Berechnung der aktuell so angeben nur Die vorherige Store müssen gespeichert werden. Die Idee ist, zwei zu schaffen 2D-Arrays prevMove[][] Und currMove[][] Wo

  • prevMove[i][j] speichert die Wahrscheinlichkeit, dass der Springer bis zum vorherigen Zug bei (i j) war. Es wird mit dem Wert 1 für den Anfangszustand initialisiert.
  • currMove[i][j] speichert die Wahrscheinlichkeit des aktuellen Zustands.

Gehen Sie ähnlich wie oben beschrieben vor und bei Ende jeder Iteration update prevMove[][] mit gespeichertem Wert currMove[][].

C++
   // C++ program to find the probability of the   // knight to remain inside the chessboard   #include          using     namespace     std  ;   // Function to find the probability   double     findProb  (  int     n       int     x       int     y       int     k  )     {      // dp to store results of previous move      vector   <  vector   <  double  >>     prevMove  (  n       vector   <  double  >  (  n       1  ));      // dp to store results of current move      vector   <  vector   <  double  >>     currMove  (  n       vector   <  double  >  (  n       0  ));      vector   <  vector   <  int  >>     directions     =     {      {  1       2  }     {  2       1  }     {  2       -1  }     {  1       -2  }         {  -1       -2  }     {  -2       -1  }     {  -2       1  }     {  -1       2  }      };      for     (  int     move     =     1  ;     move      <=     k  ;     move  ++  )     {          // find probability for cell (i j)      for     (  int     i     =     0  ;     i      <     n  ;     ++  i  )     {      for     (  int     j     =     0  ;     j      <     n  ;     ++  j  )     {      double     cur     =     0.0  ;      // for every position reachable from (xy)      for     (  auto     d  :  directions  )     {      int     u     =     i     +     d  [  0  ];      int     v     =     j     +     d  [  1  ];      // if this position lie inside the board      if     (  u     >=     0     &&     u      <     n     &&     v     >=     0     &&     v      <     n  )      cur     +=     prevMove  [  u  ][  v  ]     /     8.0  ;      }      // store the result      currMove  [  i  ][  j  ]     =     cur  ;      }      }      // update previous state      prevMove     =     currMove  ;      }      // return the result      return     prevMove  [  x  ][  y  ];   }   int     main  (){      int     n     =     8       x     =     0       y     =     0       k     =     3  ;      cout      < <     findProb  (  n       x       y       k  )      < <     endl  ;      return     0  ;   }   
Java
   // Java program to find the probability of the   // knight to remain inside the chessboard   class   GfG     {      // Function to find the probability      static     double     findProb  (  int     n       int     x       int     y       int     k  )     {      // dp to store results of previous move      double  [][]     prevMove     =     new     double  [  n  ][  n  ]  ;      for     (  int     i     =     0  ;     i      <     n  ;     i  ++  )     {      for     (  int     j     =     0  ;     j      <     n  ;     j  ++  )     {      prevMove  [  i  ][  j  ]     =     1.0  ;      }      }      // dp to store results of current move      double  [][]     currMove     =     new     double  [  n  ][  n  ]  ;      int  [][]     directions     =     {      {  1       2  }     {  2       1  }     {  2       -  1  }     {  1       -  2  }      {  -  1       -  2  }     {  -  2       -  1  }     {  -  2       1  }     {  -  1       2  }      };      for     (  int     move     =     1  ;     move      <=     k  ;     move  ++  )     {      // find probability for cell (i j)      for     (  int     i     =     0  ;     i      <     n  ;     ++  i  )     {      for     (  int     j     =     0  ;     j      <     n  ;     ++  j  )     {      double     cur     =     0.0  ;      // for every position reachable from (xy)      for     (  int  []     d     :     directions  )     {      int     u     =     i     +     d  [  0  ]  ;      int     v     =     j     +     d  [  1  ]  ;      // if this position lies inside the board      if     (  u     >=     0     &&     u      <     n     &&     v     >=     0     &&     v      <     n  )      cur     +=     prevMove  [  u  ][  v  ]     /     8.0  ;      }      // store the result      currMove  [  i  ][  j  ]     =     cur  ;      }      }      // update previous state      for     (  int     i     =     0  ;     i      <     n  ;     i  ++  )     {      System  .  arraycopy  (  currMove  [  i  ]       0       prevMove  [  i  ]       0       n  );      }      }      // return the result      return     prevMove  [  x  ][  y  ]  ;      }      public     static     void     main  (  String  []     args  )     {      int     n     =     8       x     =     0       y     =     0       k     =     3  ;      System  .  out  .  println  (  findProb  (  n       x       y       k  ));      }   }   
Python
   # Python program to find the probability of the   # knight to remain inside the chessboard   def   findProb  (  n     x     y     k  ):   # dp to store results of previous move   prevMove   =   [[  1.0  ]   *   n   for   _   in   range  (  n  )]   # dp to store results of current move   currMove   =   [[  0.0  ]   *   n   for   _   in   range  (  n  )]   directions   =   [   [  1     2  ]   [  2     1  ]   [  2     -  1  ]   [  1     -  2  ]   [  -  1     -  2  ]   [  -  2     -  1  ]   [  -  2     1  ]   [  -  1     2  ]   ]   for   move   in   range  (  1     k   +   1  ):   # find probability for cell (i j)   for   i   in   range  (  n  ):   for   j   in   range  (  n  ):   cur   =   0.0   # for every position reachable from (xy)   for   d   in   directions  :   u     v   =   i   +   d  [  0  ]   j   +   d  [  1  ]   # if this position lies inside the board   if   0    <=   u    <   n   and   0    <=   v    <   n  :   cur   +=   prevMove  [  u  ][  v  ]   /   8.0   # store the result   currMove  [  i  ][  j  ]   =   cur   # update previous state   prevMove   =   [  row  [:]   for   row   in   currMove  ]   # return the result   return   prevMove  [  x  ][  y  ]   if   __name__   ==   '__main__'  :   n     x     y     k   =   8     0     0     3   print  (  findProb  (  n     x     y     k  ))   
C#
   // C# program to find the probability of the   // knight to remain inside the chessboard   using     System  ;   class     GfG     {      // Function to find the probability      static     double     findProb  (  int     n       int     x       int     y       int     k  )     {      // dp to store results of previous move      double  []     prevMove     =     new     double  [  n       n  ];      for     (  int     i     =     0  ;     i      <     n  ;     i  ++  )      for     (  int     j     =     0  ;     j      <     n  ;     j  ++  )      prevMove  [  i       j  ]     =     1.0  ;      // dp to store results of current move      double  []     currMove     =     new     double  [  n       n  ];      int  []     directions     =     {      {  1       2  }     {  2       1  }     {  2       -  1  }     {  1       -  2  }      {  -  1       -  2  }     {  -  2       -  1  }     {  -  2       1  }     {  -  1       2  }      };      for     (  int     move     =     1  ;     move      <=     k  ;     move  ++  )     {      // find probability for cell (i j)      for     (  int     i     =     0  ;     i      <     n  ;     ++  i  )     {      for     (  int     j     =     0  ;     j      <     n  ;     ++  j  )     {      double     cur     =     0.0  ;      // for every position reachable from (xy)      for     (  int     d     =     0  ;     d      <     directions  .  GetLength  (  0  );     d  ++  )     {      int     u     =     i     +     directions  [  d       0  ];      int     v     =     j     +     directions  [  d       1  ];      // if this position lies inside the board      if     (  u     >=     0     &&     u      <     n     &&     v     >=     0     &&     v      <     n  )      cur     +=     prevMove  [  u       v  ]     /     8.0  ;      }      // store the result      currMove  [  i       j  ]     =     cur  ;      }      }      // update previous state      Array  .  Copy  (  currMove       prevMove       n     *     n  );      }      // return the result      return     prevMove  [  x       y  ];      }      static     void     Main  ()     {      int     n     =     8       x     =     0       y     =     0       k     =     3  ;      Console  .  WriteLine  (  findProb  (  n       x       y       k  ));      }   }   
JavaScript
   // JavaScript program to find the probability of the   // knight to remain inside the chessboard   function     findProb  (  n       x       y       k  )     {      // dp to store results of previous move      let     prevMove     =     Array  .  from  ({     length  :     n     }         ()     =>     Array  (  n  ).  fill  (  1.0  ));      // dp to store results of current move      let     currMove     =     Array  .  from  ({     length  :     n     }         ()     =>     Array  (  n  ).  fill  (  0.0  ));      const     directions     =     [      [  1       2  ]     [  2       1  ]     [  2       -  1  ]     [  1       -  2  ]      [  -  1       -  2  ]     [  -  2       -  1  ]     [  -  2       1  ]     [  -  1       2  ]      ];      for     (  let     move     =     1  ;     move      <=     k  ;     move  ++  )     {      // find probability for cell (i j)      for     (  let     i     =     0  ;     i      <     n  ;     i  ++  )     {      for     (  let     j     =     0  ;     j      <     n  ;     j  ++  )     {      let     cur     =     0.0  ;      // for every position reachable from (xy)      for     (  let     d     of     directions  )     {      let     u     =     i     +     d  [  0  ];      let     v     =     j     +     d  [  1  ];      // if this position lies inside the board      if     (  u     >=     0     &&     u      <     n     &&     v     >=     0     &&     v      <     n  )      cur     +=     prevMove  [  u  ][  v  ]     /     8.0  ;      }      // store the result      currMove  [  i  ][  j  ]     =     cur  ;      }      }      // update previous state      prevMove     =     currMove  .  map  (  row     =>     [...  row  ]);      }      // return the result      return     prevMove  [  x  ][  y  ].  toFixed  (  6  );   }   let     n     =     8       x     =     0       y     =     0       k     =     3  ;   console  .  log  (  findProb  (  n       x       y       k  ));   

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