Valid position in array-CodePudding

is_in_board(n : int, pos : Tuple[int, int]) -> bool Returns True if the pos position is valid for a plate of size n × n; returns False otherwise. The position pos is a pair of indices (i, j). For example, on a 7 × 7 board, position (0.5) is valid but (1.7) is not.

def extract_pos(n, str_pos):
        letters = [chr(x   ord('a')) for x in range(n)]
        numbers = [str(x) for x in range(1,n 1)]
        numbers.reverse()


         if len(str_pos) < 2 or str_pos[0] not in letters or str_pos[1] not in numbers:
         res = None

         else:

              res = (numbers.index(str_pos[1:]), letters.index(str_pos[0]))
        return res

def is_in_board(n,pos):
         letters = [chr(x   ord('a')) for x in range(n)]
         numbers = [str(x) for x in range(1, n   1)]
         numbers.reverse()
         pos = ''.join([letters[pos[1]], numbers[pos[0]]])
         if extract_pos(n,pos) is not None:
               return True
         else:
               return False

How can I return False when the list (pos) index is out of range ?board

CodePudding user response：

At the first line of the function extract_pos function you know all that you need:

The size of the plate: n x n
The desired indexes: str_pos

So I would do something like this at the first line of the extract_pos function:

if int(str_pos[0]) >= n or int(str_pos[1]) >= n or int(str_pos[0]) < 0 or int(str_pos[1]) < 0 :
    return 'Out of index'

Then you have to check that return value in the is_in_board function:

extract_pos_return_value = extract_pos(n,pos)
if extract_pos_return_value is not None and extract_pos_return_value is not 'Out of index':
    return True
else:
    return False

Full Code:

def extract_pos(n, str_pos):
        if int(str_pos[0]) >= n or int(str_pos[1]) >= n or int(str_pos[0]) < 0 or int(str_pos[1]) < 0 :
              return 'Out of index'
        letters = [chr(x   ord('a')) for x in range(n)]
        numbers = [str(x) for x in range(1,n 1)]
        numbers.reverse()


         if len(str_pos) < 2 or str_pos[0] not in letters or str_pos[1] not in numbers:
              res = None

         else:

              res = (numbers.index(str_pos[1:]), letters.index(str_pos[0]))
        return res

def is_in_board(n,pos):
         letters = [chr(x   ord('a')) for x in range(n)]
         numbers = [str(x) for x in range(1, n   1)]
         numbers.reverse()
         pos = ''.join([letters[pos[1]], numbers[pos[0]]])
         extract_pos_return_value = extract_pos(n,pos)
         if extract_pos_return_value is not None and extract_pos_return_value is not 'Out of index':
              return True
         else:
              return False

CodePudding user response：

I'll try to show you a simpler solution.

First, you do not need to construct lists for letters and for numbers, it is much easier to check the parameter.

Then in your is_in_board function you have not handled your pos parameter correctly.

Pleas check this solution:

def extract_pos(n, str_pos):
        if 0<=ord(str_pos[0])-ord('a')<n and 0<=ord(str_pos[1])-ord('0')<n:
            return ord(str_pos[0])-ord('a'), int(str_pos[1])
        else:
            return None
            
def is_in_board(n,pos):
         xpos = extract_pos(n,pos)
         if xpos != None:
             x, y = xpos
             if 0<=x<n and 0<=y<n:
               return True
         return False