Python: The eight queens puzzle/unittests: Pls do not change the codes, thank you :)

import unittest from sys import argv

''' The eight queens puzzle is the problem of placing eight chess queens on an 88 chessboard so that no two queens threaten each other. Thus, a solution requires that no two queens share the same row, column, or diagonal. The eight queens puzzle is an example of the more general n queens problem of placing n non-attacking queens on an nn chessboard, for which solutions exist for all natural numbers n with the exception of n=2 and n=3. https://en.wikipedia.org/wiki/Eight_queens_puzzle '''

# start with solving this SOLVE_ONE = True # then worry about this if you have time SOLVE_ALL = True

def safe(x1, y1, x2, y2): return not (x1 == x2 or y1 == y2 or abs(x2-x1) == abs(y2-y1))

def print_board(solution): length = len(solution) print('-' * length)

a = [['Q' if (i, j) in solution else '.' \ for j in range(length)] \ for i in range(length)] for i in a: print(''.join(i))

print('-' * length)

''' size is the overall size of the problem we're solving. row is the row we're currently on, starting with 0. placed is a list of queens -- a list of tuples with (x,y) -- that have already been placed on the board. ''' def solve_one(size, row, placed): # if we're past the last row, return placed as it has the answer. # for each column # see if placing a queen at row and column is safe from all placed # queens. # if it is safe # make a recursive call with the next row and placed + (row, column) # if there was a solution with those parameters, return it. # return the empty list pass

''' as above, but accumulate all the solutions in the last argument. ''' def solve_all(size, row, placed, solutions): pass

class test_safe(unittest.TestCase): def test_same(self): self.assertFalse(safe(1, 1, 1, 1)) def test_same_row(self): self.assertFalse(safe(1, 1, 1, 2)) def test_same_column(self): self.assertFalse(safe(1, 1, 2, 1)) def test_same_diagonal(self): self.assertFalse(safe(1, 1, 5, 5))

class test_one(unittest.TestCase): def test_one_one(self): self.assertEqual(solve_one(1, 0, []), [(0, 0)]) def test_two_all(self): self.assertEqual(solve_one(2, 0, []), []) def test_four_one(self): self.assertEqual(solve_one(4, 0, []), [(0, 1), (1, 3), (2, 0), (3, 2)])

''' class test_all(unittest.TestCase): def test_one_all(self): self.assertEqual(solve_all(1, 0, [], []), [[(0, 0)]]) def test_two_all(self): self.assertEqual(solve_all(2, 0, [], []), []) def test_three_all(self): self.assertEqual(solve_all(3, 0, [], []), []) def test_four_all(self): solutions = solve_all(4, 0, [], []) self.assertEqual(solutions, [[(0, 1), (1, 3), (2, 0), (3, 2)], \ [(0, 2), (1, 0), (2, 3), (3, 1)]]) '''

if __name__ == "__main__": size = 8 if len(argv) == 1 else int(argv[1])

if SOLVE_ONE: print_board(solve_one(size, 0, [])) if SOLVE_ALL: solutions = [] solve_all(size, 0, [], solutions) print("there are", len(solutions), "solutions for the", \ size, "queens problem:") for solution in solutions: print_board(solution)