Question

How can I get my Python code to check to make sure there are no ships overlapping in my Battleship code?

I am having a really hard time with a game of battleship that I have due for class. Each time I run my code, It will print the ships on the board but it will at times overlap them. I know I have to use some kind of nested if statements but I just don't get how or where I would do this at. Here is my code so far.

#This makes the board
import random
board = []
for i in range(0,10):
    board.append(['0'] *10)
def print_board(board):
    for row in board:
        print((" ").join(row))


ship={'S':5,'A':4,'B':3,'C':3,'D':2}

for i, j in ship.items():
    row = random.randint(0, len(board) - j)
    col= random.randint(0, len(board) - j)
    for k in range(j):
        board[row][col+k] = i
        
            

print_board(board)

Here is what happens when I print it out:

0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 C C C 0 0
0 S S S S S 0 0 0 0
0 B B B 0 0 0 0 0 0
0 0 0 A A D D 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0

As you can see, D overlapped A in this example. What I would like the code to do is before it places the letters down I want it to check and if the there is a letter where it is trying to place to try using a different position. Then if that doesn't work just try a whole new section. so far the only thing I can think of for a code is something like this:

for i, j in ship.items():
    row = random.randint(0, len(board) - j)
    col = random.randint(0, len(board)- j)
    for k in range(j):
        if board[row][col+k] != '0':
            if board[row+k][col] != '0':
                if board[row+k][col+k] != '0':
                    x = random.randint(0, len(board) - j)
                    y = random.randint(0, len(board)- j)
                else:
                    board[row+k][col+k] = i
            else:
                board[row+k][col] = i
        else:
            board[row][col+k] = i

print_board(board)

which when I try this code it get me results like this:

D D 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 A A A A C 0 0
0 0 0 0 0 C 0 0 0 0
S S S S S 0 0 0 0 0
0 B 0 0 0 0 0 0 0 0
0 B 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0

I am still getting overlaps and now my ships are snapping in half like what happened with C.

Am I just completely off base with my thought? Or am I just missing some big key parts?

Answer 1

Hi, Here is the code which works correctly to insert the 5 battleships in the grid, in either horizontal or vertical position, with no overlap.

I have used most of your code as-is. It was buggy in the logic of checking whether you have enough free squares either horizontally or vertically for the selected random row and col. You were checking through an "if" condition, but it has to be a "while" loop which has to keep on trying till it finds the free set of squares.

So I added an infinite while loop (while True) which will check if the selected row and col have free squares to accommodate the ship - first check horizontally, if not available check vertically. If space is available, it will exit the while loop and insert the ship into the grid at the row and col (either horizontally or vertically based on where it found the space)

I have added the comments in the code. Look for the new code between the #added comment lines which is new. The while loop and 3 boolean flags are also newly added.

Have tested it quite a few times and it is working. You can try to further optimize the code if you wish.

Complete program is given below.

------------

#This makes the board
import random
board = []
for i in range(0,10):
board.append(['0'] *10)
  
def print_board(board):
for row in board:
print((" ").join(row))

ship={'S':5,'A':4,'B':3,'C':3,'D':2}

for i, j in ship.items():
while True:
'''
added 3 booleans
found = to indicate whether we were able to find free squares to fit the ship
used as a boolean to exit from loop
vertical = flag to indicate if the free squares are vertical
horizontal = flag to indicate if the free squares are horizontal
Logic of the while loop:
program will first check for horizontal free squares. If found, it
will exit the while loop after setting horizontal = True
Else, it will check for vertical free squares. If found, it will exit
the while loop after setting vertical = True
If neither vertical nor horizontal is found, the infinite while loop
will continue with another set of random choices for row and col
'''
found = True
vertical = False
horizontal = False
row = random.randint(0, len(board) - j)
col= random.randint(0, len(board) - j)
#added code to check for free squares here
#check horizontally if k squares are free from the selected row
for k in range(j):
if board[row][col+k] != '0': #occupied
found = False
break
if (found):
#this means that the earlier for loop exited after finding free space
#hence we can exit the while loop. Else the infinite while loop will continue
horizontal = True
break
#horizontal not free, so check vertically if k squares are free
found = True
for k in range(j):
if board[row+k][col] != '0': #occupied
found = False
break
if (found):
#this means that the earlier for loop exited after finding free space
#hence we can exit the while loop. Else the infinite while loop will continue
vertical = True
break
#end addition
  
#now we are out of while loop after confirming that the squares are free, so update
if (horizontal):
for k in range(j):
board[row][col+k] = i
elif (vertical):
for k in range(j):
board[row+k][col] = i
  
  
  
print_board(board)