Add solution for connect4

src/python/katas/py5kyu/connect4.py

@@ -0,0 +1,58 @@
+"""Kata url: https://www.codewars.com/kata/586c0909c1923fdb89002031."""
+
+
+class Connect4:
+
+    def __init__(self):
+        self.width = 6
+        self.height = 7
+
+        self.board = [list("-")*self.width for _ in range(self.height)]
+        self.placed = [0]*self.height
+        self.turn = 1
+
+        self.visited = [[False]*self.width for _ in range(self.height)]
+        self.won = False
+
+    @property
+    def player(self):
+        return "YR"[self.turn & 1]
+
+    def count_connected(self, x, y, dirs) -> int:
+        if x < 0 or x >= self.width or y < 0 or y >= self.height:
+            return 0
+
+        if self.visited[y][x] or self.board[y][x] != self.player:
+            return 0
+
+        self.visited[y][x] = True
+        count = 1 # this one!
+
+        for (dx, dy) in dirs:
+            count += self.count_connected(x + dx, y + dy, dirs)
+
+        self.visited[y][x] = False
+        return count
+
+    def play(self, col):
+        if self.won:
+            return "Game has finished!"
+        x = self.placed[col]
+        if x == self.width:
+            return "Column full!"
+
+        self.turn ^= 1
+        self.board[col][x] = self.player
+        self.placed[col] += 1
+
+        for dirs in (
+            ((-1, 0), (1, 0)),
+            ((0, -1), (0, 1)),
+            ((-1, -1), (1, 1)),
+            ((1, -1), (-1, 1))
+        ):
+            if self.count_connected(x, col, dirs) >= 4:
+                self.won = True
+                return f"Player {self.turn + 1} wins!"
+
+        return f"Player {self.turn + 1} has a turn"