Win condition checking in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a player has won by filling the blank.

LLD

if board[row][col] == [1]:
    return True

Drag options to blanks, or click blank then click option'

Aplayer_symbol

Bempty_cell

Copponent_symbol

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Using empty_cell instead of player_symbol

Checking for opponent_symbol instead of player_symbol

The win condition checks if the current cell matches the player's symbol.

2fill in blank

medium

Complete the code to count consecutive symbols in a row.

LLD

count = 0
for c in range(len(board[0])):
    if board[row][c] == [1]:
        count += 1

Drag options to blanks, or click blank then click option'

Aempty_cell

Bplayer_symbol

Copponent_symbol

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Counting empty cells instead of player symbols

Counting opponent symbols by mistake

We count cells matching the player's symbol to check for a win in the row.

3fill in blank

hard

Fix the error in the diagonal win check by filling the blank.

LLD

for i in range(size):
    if board[i][i] != [1]:
        return False
return True

Drag options to blanks, or click blank then click option'

Aempty_cell

Bopponent_symbol

CNone

Dplayer_symbol

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for empty cells instead of player symbols

Checking for opponent symbols

The diagonal must have all cells matching the player's symbol to win.

4fill in blank

hard

Fill both blanks to check vertical win condition correctly.

LLD

for r in range(size):
    if board[r][col] != [1]:
        return False
return [2]

Drag options to blanks, or click blank then click option'

Aplayer_symbol

BTrue

CFalse

Dempty_cell

Attempts:

3 left

💡 Hint

Common Mistakes

Returning False instead of True after the loop

Checking for empty cells instead of player symbols

Check each cell in the column for the player's symbol; if all match, return True.

5fill in blank

hard

Fill all three blanks to complete the function that checks horizontal, vertical, and diagonal wins.

LLD

def check_win(board, player):
    size = len(board)
    for i in range(size):
        if all(board[i][j] == [1] for j in range(size)):
            return [2]
        if all(board[j][i] == [1] for j in range(size)):
            return [2]
    if all(board[i][i] == [1] for i in range(size)):
        return [2]
    if all(board[i][size - 1 - i] == [1] for i in range(size)):
        return [2]
    return [3]

Drag options to blanks, or click blank then click option'

Aplayer

BTrue

CFalse

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Returning None instead of False when no win

Checking wrong symbols in conditions

The function checks all win conditions for the player symbol and returns True if any are met, otherwise False.

Practice

1. What is the primary purpose of win condition checking in a game system?

easy

A. To update the player's score after each move

B. To determine if a player has won the game by matching symbols in a row, column, or diagonal

C. To reset the game board after a draw

D. To display the game instructions to the player

Solution

1. Step 1: Understand the role of win condition checking

   Win condition checking is used to decide if the game has ended with a winner by checking patterns on the board.

2. Step 2: Identify the correct purpose among options

   Only To determine if a player has won the game by matching symbols in a row, column, or diagonal describes checking rows, columns, or diagonals for matching symbols to declare a winner.

3. Final Answer:

   To determine if a player has won the game by matching symbols in a row, column, or diagonal -> Option B

4. Quick Check:

   Win condition checking = Determine winner [OK]

Hint: Win condition means checking if someone won the game [OK]

Common Mistakes:

• Confusing win checking with score updating
• Thinking it resets the game board
• Assuming it shows instructions

2. Which of the following code snippets correctly checks a row for a win in a 3x3 tic-tac-toe board represented as a 2D array board?

easy

A. if board[row][0] != board[row][1] != board[row][2]:

B. if board[0][row] == board[1][row] == board[2][row] != None:

C. if board[row][0] == board[row][1] == board[row][2] != None:

D. if board[0][0] == board[1][1] == board[2][2] != None:

Solution

1. Step 1: Identify row checking syntax

   Checking a row means comparing all elements in the same row index but different columns.

2. Step 2: Match code to row check

   if board[row][0] == board[row][1] == board[row][2] != None: compares board[row][0], board[row][1], and board[row][2], which is correct for a row check.

3. Final Answer:

   if board[row][0] == board[row][1] == board[row][2] != None: -> Option C

4. Quick Check:

   Row check = compare same row elements [OK]

Hint: Row check compares same row, different columns [OK]

Common Mistakes:

• Mixing row and column indices
• Using != instead of == for equality
• Checking diagonal instead of row

3. Given the following 3x3 board state:

board = [["X", "O", "X"],
         ["O", "X", "O"],
         ["O", "X", "X"]]

Which of these checks will correctly identify a win for 'X' on the main diagonal?

medium

A. board[0][0] == board[1][1] == board[2][2] == "X"

B. board[0][2] == board[1][1] == board[2][0] == "X"

C. board[0][0] == board[0][1] == board[0][2] == "X"

D. board[2][0] == board[2][1] == board[2][2] == "X"

Solution

1. Step 1: Identify main diagonal positions

   Main diagonal cells are at positions (0,0), (1,1), and (2,2).

2. Step 2: Check which option matches main diagonal and 'X'

   board[0][0] == board[1][1] == board[2][2] == "X" compares these exact positions to 'X', correctly checking the main diagonal win.

3. Final Answer:

   board[0][0] == board[1][1] == board[2][2] == "X" -> Option A

4. Quick Check:

   Main diagonal check = positions (0,0),(1,1),(2,2) [OK]

Hint: Main diagonal is top-left to bottom-right [OK]

Common Mistakes:

• Confusing main diagonal with anti-diagonal
• Checking wrong row or column
• Using equality with wrong symbol

4. Consider this code snippet for checking a column win:

def check_column(board, col):
    return board[0][col] == board[1][col] == board[2][col]

What is the main issue with this code when used for win condition checking?

medium

A. It only checks rows, not columns

B. It uses incorrect indices for columns

C. It returns a list instead of a boolean

D. It does not check if the cells are not empty or None

Solution

1. Step 1: Analyze the equality check

   The code checks if all three cells in the column are equal but does not verify if they are non-empty.

2. Step 2: Identify missing condition for valid win

   Without checking for None or empty, it may falsely report a win if all cells are empty.

3. Final Answer:

   It does not check if the cells are not empty or None -> Option D

4. Quick Check:

   Check for non-empty cells to confirm win [OK]

Hint: Always check cells are not empty before confirming win [OK]

Common Mistakes:

• Ignoring empty or None cells in equality
• Mixing row and column indices
• Expecting a list return instead of boolean

5. You are designing a scalable win condition checker for an n x n board game. Which approach best balances efficiency and scalability?

hard

A. Only check the row, column, and diagonals related to the last move

B. Check all rows, columns, and both diagonals after every move

C. Check the entire board for a winner after every move

D. Check only the diagonals after every move

Solution

1. Step 1: Understand the cost of checking all lines

   Checking all rows, columns, and diagonals after every move is expensive for large boards.

2. Step 2: Focus on last move's related lines

   Only the row, column, and diagonals that include the last move can change the win state, so checking these is efficient and scalable.

3. Final Answer:

   Only check the row, column, and diagonals related to the last move -> Option A

4. Quick Check:

   Check only affected lines after move for efficiency [OK]

Hint: Check only lines affected by last move for best performance [OK]

Common Mistakes:

• Checking entire board every time wastes resources
• Ignoring diagonals in win checking
• Checking unrelated rows or columns