Ticket #168: draqo-send2ret1a.diff

engine/utils.c

@@ -1426 +1426 @@
   int other = OTHER_COLOR(color);
   int lib1;
   int lib2;
+  int neighbor;
 
+  /* We must check this, because in such position:
+   *
+   * -----
+   * O.*OX
+   * OOXXX
+   *
+   * move * prevents making an eye by X player.
+   */
+  neighbor = find_neighbor(move, color);
+  if (neighbor == NO_MOVE || countlib(neighbor) != 2)
+    return 0;
+
   /* Try to play the move. */
   if (!trymove(move, color, "send_two_return_one-A", NO_MOVE))
     return 0;

engine/board.c

@@ -2873 +2873 @@
           || board[EAST(pos)] == color);
 }
 
+/* If (pos) has exactly one neighbor of color (color)
+ * returns position of this neighbor. Otherwise returns NO_MOVE.
+ */
+
+int
+find_neighbor(int pos, int color)
+{
+  int npos = NO_MOVE;
+
+  ASSERT_ON_BOARD1(pos);
+  ASSERT1(IS_STONE(color), pos);
+
+  if (board[SOUTH(pos)] == color)
+    npos = SOUTH(pos);
+
+  if (board[WEST(pos)] == color) {
+    if (npos != NO_MOVE)
+      return NO_MOVE;
+    else
+      npos = WEST(pos);
+  }
+
+  if (board[NORTH(pos)] == color) {
+    if (npos != NO_MOVE)
+      return NO_MOVE;
+    else
+      npos = NORTH(pos);
+  }
+
+  if (board[EAST(pos)] == color) {
+    if (npos != NO_MOVE)
+      return NO_MOVE;
+    else
+      npos = EAST(pos);
+  }
+
+  return npos;
+}
+
 /*
  * Returns true if str1 and str2 belong to the same string.
  */

engine/board.h

@@ -323 +323 @@
 int second_order_liberty_of_string(int pos, int str);
 int neighbor_of_string(int pos, int str);
 int has_neighbor(int pos, int color);
+int find_neighbor(int pos, int color);
 int same_string(int str1, int str2);
 int adjacent_strings(int str1, int str2);
 void mark_string(int str, signed char mx[BOARDMAX], signed char mark);