connect: Implement the exercise "connect"

config.json

@@ -1021,6 +1021,17 @@
         "text_formatting"
       ]
     },
+    {
+      "uuid": "f5503274-ac23-11e7-abc4-cec278b6b50a",
+      "slug": "connect",
+      "core": false,
+      "unlocked_by": null,
+      "difficulty": 1,
+      "topics": [
+        "parsing",
+        "transforming"
+      ]
+    },
     {
       "uuid": "33f689ee-1d9c-4908-a71c-f84bff3510df",
       "slug": "collatz-conjecture",

exercises/connect/README.md

@@ -0,0 +1,44 @@
+# Connect
+
+Compute the result for a game of Hex / Polygon.
+
+The abstract boardgame known as
+[Hex](https://en.wikipedia.org/wiki/Hex_%28board_game%29) / Polygon /
+CON-TAC-TIX is quite simple in rules, though complex in practice. Two players
+place stones on a rhombus with hexagonal fields. The player to connect his/her
+stones to the opposite side first wins. The four sides of the rhombus are
+divided between the two players (i.e. one player gets assigned a side and the
+side directly opposite it and the other player gets assigned the two other
+sides).
+
+Your goal is to build a program that given a simple representation of a board
+computes the winner (or lack thereof). Note that all games need not be "fair".
+(For example, players may have mismatched piece counts.)
+
+The boards look like this (with spaces added for readability, which won't be in
+the representation passed to your code):
+
+```
+. O . X .
+ . X X O .
+  O O O X .
+   . X O X O
+    X O O O X
+```
+
+"Player `O`" plays from top to bottom, "Player `X`" plays from left to right. In
+the above example `O` has made a connection from left to right but nobody has
+won since `O` didn't connect top and bottom.
+
+### Submitting Exercises
+
+Note that, when trying to submit an exercise, make sure the solution is in the `exercism/python/<exerciseName>` directory.
+
+For example, if you're submitting `bob.py` for the Bob exercise, the submit command would be something like `exercism submit <path_to_exercism_dir>/python/bob/bob.py`.
+
+
+For more detailed information about running tests, code style and linting,
+please see the [help page](http://exercism.io/languages/python).
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

exercises/connect/connect.py

@@ -0,0 +1,7 @@
+
+class ConnectGame:
+    def __init__(self, board):
+        pass
+
+    def get_winner(self):
+        pass

exercises/connect/connect_test.py

@@ -0,0 +1,118 @@
+import unittest
+
+import connect
+
+
+# Tests adapted from `problem-specifications//canonical-data.json` @ v1.1.0
+
+testcases = [
+    {
+        "description": "an empty board has no winner",
+        "board":
+        """ . . . . .
+             . . . . .
+              . . . . .
+               . . . . .
+                . . . . .""",
+        "winner": ""
+    },
+    {
+        "description": "O can win on a 1x1 board",
+        "board": "O",
+        "winner": "O"
+    },
+    {
+        "description": "X can win on a 1x1 board",
+        "board": "X",
+        "winner": "X"
+    },
+    {
+        "description": "only edges does not make a winner",
+        "board":
+            """ O O O X
+                 X . . X
+                  X . . X
+                   X O O O""",
+        "winner": ""
+    },
+    {
+        "description": "illegal diagonal does not make a winner",
+        "board":
+            """ X O . .
+                 O X X X
+                  O X O .
+                   . O X .
+                    X X O O""",
+        "winner": ""
+    },
+    {
+        "description": "nobody wins crossing adjacent angles",
+        "board":
+            """ X . . .
+                 . X O .
+                  O . X O
+                   . O . X
+                    . . O .""",
+        "winner": ""
+    },
+    {
+        "description": "X wins crossing from left to right",
+        "board":
+            """ . O . .
+                 O X X X
+                  O X O .
+                   X X O X
+                    . O X .""",
+        "winner": "X"
+    },
+    {
+        "description": "X wins using a convoluted path",
+        "board":
+            """ . X X . .
+                 X . X . X
+                  . X . X .
+                   . X X . .
+                    O O O O O""",
+        "winner": "X"
+    },
+    {
+        "description": "O wins crossing from top to bottom",
+        "board":
+            """ . O . .
+                 O X X X
+                  O O O .
+                   X X O X
+                    . O X .""",
+        "winner": "O"
+    },
+    {
+        "description": "X wins using a spiral path",
+        "board":
+            """ O X X X X X X X X
+                 O X O O O O O O O
+                  O X O X X X X X O
+                   O X O X O O O X O
+                    O X O X X X O X O
+                     O X O O O X O X O
+                      O X X X X X O X O
+                       O O O O O O O X O
+                        X X X X X X X X O """,
+        "winner": "X"
+    },
+]
+
+
+class ConnectTest(unittest.TestCase):
+    def test_game(self):
+        for testcase in testcases:
+            game = connect.ConnectGame(testcase["board"])
+            winner = game.get_winner()
+            expected = testcase["winner"] if testcase["winner"] else "None"
+            got = winner if winner else "None"
+            self.assertEqual(winner, testcase["winner"],
+                             "Test failed: %s, expected winner: %s, got: %s"
+                             % (testcase["description"], expected, got))
+
+
+if __name__ == '__main__':
+    unittest.main()

exercises/connect/example.py

@@ -0,0 +1,61 @@
+
+class ConnectGame:
+
+    directions = [(0, 1), (0, -1), (1, 0), (-1, 0), (1, -1), (-1, 1)]
+    white = "O"
+    black = "X"
+    none = ""
+
+    def __init__(self, lines):
+        self.board = self.make_board(lines)
+        assert len(self.board) > 0
+
+        self.width = len(self.board[0])
+        self.height = len(self.board)
+        assert self.width > 0 and self.height > 0
+
+        for l in self.board:
+            assert len(l) == self.width
+
+    def valid(self, x, y):
+        return x >= 0 and x < self.width and y >= 0 and y < self.height
+
+    def make_board(self, lines):
+        return ["".join(l.split()) for l in lines.splitlines()]
+
+    def player_reach_dest(self, player, x, y):
+        if player == self.black:
+            return x == self.width - 1
+        if player == self.white:
+            return y == self.height - 1
+
+    def walk_board(self, player, x, y, visited=[]):
+        if (x, y) in visited:
+            return False
+
+        if (not self.valid(x, y)) or self.board[y][x] != player:
+            return False
+
+        if self.player_reach_dest(player, x, y):
+            return True
+
+        for d in self.directions:
+            if self.walk_board(player, x + d[0], y + d[1], visited + [(x, y)]):
+                return True
+
+    def check_player_is_winner(self, player):
+        if player == self.black:
+            for y in range(self.height):
+                if self.walk_board(player, 0, y):
+                    return True
+        if player == self.white:
+            for x in range(self.width):
+                if self.walk_board(player, x, 0):
+                    return True
+
+    def get_winner(self):
+        if self.check_player_is_winner(self.black):
+            return self.black
+        if self.check_player_is_winner(self.white):
+            return self.white
+        return self.none