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Author: ziennaa

GAMES/sudoku_game.py

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+import random # imports random to pick random numbers and shuffle cells
+import sys # calls sys.exit() so program can end whenver user quits
+# function to print the board
+def print_board(board):
+    '''
+    displays 9*9 board in a formatted grid
+    with lines separating 3*3 subgrids basically 2d list board 9*9
+    '''
+    for i in range(9):
+        if i % 3 == 0 and i != 0:
+            print("- - - - - - - - - - - - - - -")
+            '''
+            every time i is a multiple of 3 it print horizontal seperator
+            this is row index or used for maing row
+            '''
+        for j in range(9):
+          '''
+          every time j is multiple of 3, we print vertical bars without
+          for coloumns
+          '''
+          if j % 3 == 0 and j != 0:
+                print("|", end=" ")
+          print(board[i][j] if board[i][j] != 0 else ".", end=" ")
+            # prints cells value if nonzero otherwise . to make empty cell
+            # on the same line end=" "
+        print() # for moving to next line
+
+# function to find an empty cell in board
+def find_empty(board):# searches the grid
+    for i in range(9):
+        for j in range(9):
+          # used for scanning every row i and every col j to look for 0(indicates empty)
+            if board[i][j] == 0:
+                return (i, j) # returns row and col as soon as it finds empty 
+    return None
+
+# function to check if placing num at pos is valid
+def is_valid(board, num, pos):# check if you can place a number at row or col
+    row, col = pos
+    if any(board[row][i] == num for i in range(9) if i != col): #scaNS row for duplicates
+        return False
+    if any(board[i][col] == num for i in range(9) if i != row): # scans entire col for duplicates
+        return False
+    box_row = (row // 3) * 3
+    box_col = (col // 3) * 3
+    for i in range(box_row, box_row + 3):
+        for j in range(box_col, box_col + 3):
+            if board[i][j] == num and (i, j) != pos:
+                return False # if num appears somewhere else move illegal
+    return True # if not true
+
+# Backtracking solver
+def solve_board(board):
+  # here function find empty and is valid is used 
+  # to fill the board , it tries all numbers from 1 to 9 at each empty cell and proceeds only if valid
+    empty = find_empty(board)
+    if not empty:
+        return True
+    row, col = empty
+    for num in range(1, 10):
+        if is_valid(board, num, (row, col)):
+            board[row][col] = num
+            if solve_board(board):
+                return True
+            board[row][col] = 0
+    return False
+
+def count_solutions(board):
+  # counts all possible ways to create or complete the solutuion 
+  # no empty you found sol and returns 1
+  # and finds total num of solution and stores in count
+    empty = find_empty(board)
+    if not empty:
+        return 1
+    row, col = empty
+    count = 0
+    for num in range(1, 10):
+        if is_valid(board, num, (row, col)):
+            board[row][col] = num
+            count += count_solutions(board)
+            board[row][col] = 0
+    return count
+
+def create_board(removals=30):
+   # creates an empty board
+# num cell is used to choose difficulty
+# here removal check that only 1 unique sol remains using count_solutions
+    board = [[0]*9 for _ in range(9)]
+    solve_board(board)
+    removed = 0
+    while removed < removals:
+        r = random.randrange(9)
+        c = random.randrange(9)
+        if board[r][c] != 0:
+            temp = board[r][c]
+            board[r][c] = 0
+            copy = [row[:] for row in board]
+            if count_solutions(copy) != 1:
+                board[r][c] = temp
+            else:
+                removed += 1
+    return board
+
+def is_complete(board):
+    return all(cell != 0 for row in board for cell in row)
+    # returns if every cell in grid is non zero
+
+def get_input(prompt):
+    while True:
+        inp = input(prompt)
+        if inp.lower() == 'q': # q to exit the program
+            sys.exit("Goodbye!")
+        if inp.isdigit() and 1 <= int(inp) <= 9:
+            return int(inp) - 1
+        print("Invalid input. Enter 1-9 or 'q'.")
+
+def player_turn(board):
+    print("\n your move:")
+    print_board(board)
+    while True:
+        row = get_input("Enter row (1-9) or 'q' to quit: ")
+        col = get_input("Enter column (1-9) or 'q' to quit: ")
+        if board[row][col] == 0:
+            break
+        print("choose another, cell already filled")
+    while True:
+        num = get_input("Enter number (1-9) or 'q' to quit: ") + 1
+        if is_valid(board, num, (row, col)):
+            board[row][col] = num
+            break
+        print("invalid try again")
+
+def computer_turn(board):
+    print("\nComputer's move:")
+    print_board(board)
+    empties = [(i, j) for i in range(9) for j in range(9) if board[i][j] == 0]
+    random.shuffle(empties)
+    for row, col in empties:
+        for num in range(1, 10):
+            if is_valid(board, num, (row, col)):
+                board[row][col] = num
+                if count_solutions([r[:] for r in board]) == 1:
+                    print(f"Computer placed {num} at ({row+1},{col+1})")
+                    return
+                board[row][col] = 0
+    print("computer gives up. multiple solutions possible.")
+
+if __name__ == "__main__":
+    puzzle = create_board(removals=30)
+    while True:
+        player_turn(puzzle)
+        cont = input("\nPress 't' if tired and let computer solve it, any other key to continue: ")
+        if cont.lower() == 't':
+            solve_board(puzzle)
+            print_board(puzzle)
+            print("\n Computer has solved the rest of the puzzle :(( Game over.")
+            break
+        if is_complete(puzzle):
+            print_board(puzzle)
+            print("Congratulations! You solved it!!!!")
+            break
+        computer_turn(puzzle)
+        if is_complete(puzzle):
+            print_board(puzzle)
+            print("Computer solved it!! You lose!!!!")
+            break