Create Sudoku_Solver.py

Author: sksalahuddin2828

Sudoku_Solver.py

@@ -0,0 +1,92 @@
+# Size of the 2D matrix (N x N)
+# grid_size = N / means N = 9
+grid_size = 9 
+
+# A utility function to print the grid
+def print_grid(grid):
+ for row in range(grid_size):
+ for col in range(grid_size):
+ print(grid[row][col], end=" ")
+ print()
+
+# Checks whether it will be legal to assign num to the given row, col
+def is_safe(grid, row, col, num):
+ # Check if we find the same num in the same row, return False
+ for check_col in range(grid_size):
+ if grid[row][check_col] == num:
+ return False
+
+ # Check if we find the same num in the same column, return False
+ for check_row in range(grid_size):
+ if grid[check_row][col] == num:
+ return False
+
+ # Check if we find the same num in the particular 3x3 matrix, return False
+ start_row = row - row % 3
+ start_col = col - col % 3
+ for check_row in range(3):
+ for check_col in range(3):
+ if grid[check_row + start_row][check_col + start_col] == num:
+ return False
+ return True
+
+# Takes a partially filled-in grid and attempts to assign values to all unassigned locations
+def solve_sudoku(grid, row, col):
+ # Check if we have reached the last row and column, return True to avoid further backtracking
+ if row == grid_size - 1 and col == grid_size:
+ return True
+
+ # Check if column value becomes grid_size, move to the next row and column start from 0
+ if col == grid_size:
+ row += 1
+ col = 0
+
+ # Check if the current position of the grid already contains a value > 0, iterate for the next column
+ if grid[row][col] > 0:
+ return solve_sudoku(grid, row, col + 1)
+
+ for num in range(1, grid_size + 1):
+ # Check if it is safe to place the num (1-9) in the given row, col
+ if is_safe(grid, row, col, num):
+ # Assign the num in the current (row, col) position of the grid and assume it is correct
+ grid[row][col] = num
+
+ # Check for the next possibility with the next column
+ if solve_sudoku(grid, row, col + 1):
+ return True
+
+ # If the assumption was wrong, remove the assigned num and go for the next assumption with a different num value
+ grid[row][col] = 0
+
+ return False
+
+# Driver Code
+# 0 means unassigned cells
+grid = [
+ [3, 0, 6, 5, 0, 8, 4, 0, 0],
+ [5, 2, 0, 0, 0, 0, 0, 0, 0],
+ [0, 8, 7, 0, 0, 0, 0, 3, 1],
+ [0, 0, 3, 0, 1, 0, 0, 8, 0],
+ [9, 0, 0, 8, 6, 3, 0, 0, 5],
+ [0, 5, 0, 0, 9, 0, 6, 0, 0],
+ [1, 3, 0, 0, 0, 0, 2, 5, 0],
+ [0, 0, 0, 0, 0, 0, 0, 7, 4],
+ [0, 0, 5, 2, 0, 6, 3, 0, 0]
+]
+
+if solve_sudoku(grid, 0, 0):
+ print_grid(grid)
+else:
+ print("No solution exists.")
+
+#----------------------------------------------------------------------------------------------------------------------------------------------------------
+ 
+# Answer: 3 1 6 5 7 8 4 9 2 
+# 5 2 9 1 3 4 7 6 8 
+# 4 8 7 6 2 9 5 3 1 
+# 2 6 3 4 1 5 9 8 7 
+# 9 7 4 8 6 3 1 2 5 
+# 8 5 1 7 9 2 6 4 3 
+# 1 3 8 9 4 7 2 5 6 
+# 6 9 2 3 5 1 8 7 4 
+# 7 4 5 2 8 6 3 1 9