ksylvan · June 11, 2020 22:46 · Jun 11, 2020 · Jun 11, 2020
diff --git a/mines.py b/mines.py
@@ -103,3 +103,43 @@ def __setitem__(self, k, v):
     print(f"{r}X{c} Grid with {m} mines:\n")
     print(o)
     print("")
+
+# Sample output:
+#
+# 16X12 Grid with 4 mines:
+#
+# 11..........
+# X1..........
+# 11..........
+# ............
+# ............
+# ............
+# ............
+# ............
+# ...111......
+# ...1X1......
+# ...222......
+# ...1X1......
+# ...111......
+# ............
+# .111........
+# .1X1........
+#
+# 8X8 Grid with 5 mines:
+#
+# 11..111.
+# X1..1X21
+# 11.1222X
+# ...1X111
+# ...111..
+# ........
+# ......11
+# ......1X
+#
+# 5X5 Grid with 20 mines:
+#
+# XX4XX
+# XX7XX
+# XXXXX
+# XXXXX
+# X434X
diff --git a/mines.py b/mines.py
@@ -0,0 +1,105 @@
+from random import randrange
+
+class MinesGrid:
+  # Implement a sparse array to optimize space.
+  MINE = -1
+
+  class Row:
+    # Each row in the __a dict has the following
+    # structure a list, containing:
+    # [ empty_cells, {} ]
+    def __init__(self, cols):
+      self.__cols = cols
+      self.__empty_cells = list(range(cols))
+      self.__r = {}
+    def __str__(self):
+      d = { MinesGrid.MINE: 'X', 0: '.' }
+      return "".join(map(str,
+        (d[self[i]] if self[i] in d else self[i]
+          for i in range(self.__cols))))
+    def __repr__(self):
+      return f"Row(cols={self.__cols}, empty_cells={self.__empty_cells}, r={self.__r})"
+    def __getitem__(self, k):
+      return self.__r[k] if k in self.__r else 0
+    def __setitem__(self, k, v):
+      if k not in self.__r:
+        if k not in self.__empty_cells:
+          raise ValueError(f"{k} is not in a valid range.")
+      if v == MinesGrid.MINE:
+        self.__empty_cells.remove(k)
+      self.__r[k] = v
+    @property
+    def number_empty(self):
+      return len(self.__empty_cells)
+    @property
+    def random_cell(self):
+      if l := self.number_empty:
+        r = randrange(l)
+        return self.__empty_cells[r]
+      return None
+
+  class Empty:
+    def __getitem__(self, k):
+      return 0
+
+  def __init__(self, rows, cols, mines):
+    if rows <= 0 or cols <= 0:
+      raise ValueError(f"rows and columns need to be positive integers. rows={rows}, cols={cols}")
+    if mines > rows * cols:
+      raise ValueError(f"Too many mines: {mines}")
+    self.__rows = rows
+    self.__cols = cols
+    self.__empty = rows * cols
+    self.__a = {} # This a a dict of Row objects
+    self.__empty_row = MinesGrid.Empty()
+    for _ in range(mines):
+      self.__place_mine()
+
+  def __repr__(self):
+    return f"MinesGrid(rows={self.__rows}, cols={self.__cols}, empty={self.__empty}, rows={self.__a}"
+
+  def __str__(self):
+    empty = "." * self.__cols
+    return "\n".join(empty if r not in self.__a else str(self.__a[r])
+      for r in range(self.__rows))
+
+  def __place_mine(self):
+    if self.__empty:
+      r = randrange(self.__rows)
+      while r in self.__a and self.__a[r].number_empty == 0:
+        r = (r + 1) % self.__cols
+
+      if r not in self.__a:
+        self.__a[r] = MinesGrid.Row(self.__cols)
+
+      c = self.__a[r].random_cell
+      self.__a[r][c] = MinesGrid.MINE
+      self.__update_counts(r, c)
+      self.__empty -= 1
+
+  def __update_counts(self, r, c):
+    t = (
+      (-1,-1), (-1, 0), (-1, 1),
+      (0, -1), (0, 1),
+      (1, -1), (1, 0), (1, 1))
+    for t1, t2 in t:
+      if 0 <= r+t1 < self.__rows and 0 <= c+t2 < self.__cols:
+        u_r, u_c = r+t1, c+t2
+        if u_r not in self.__a:
+          self.__a[u_r] = MinesGrid.Row(self.__cols)
+        if self.__a[u_r][u_c] != MinesGrid.MINE:
+          self.__a[u_r][u_c] += 1
+
+  def __getitem__(self, k):
+    return self.__a[k] if k in self.__a else self.__empty_row
+
+  def __setitem__(self, k, v):
+    self.__a[k] = v
+
+if __name__ == "__main__":
+  tests = ((16, 12, 4), (8, 8, 5), (5,5, 20))
+  for r,c,m in tests:
+    o = MinesGrid(r, c, m)
+    print(f"{r}X{c} Grid with {m} mines:\n")
+    print(o)
+    print("")