From d5999adad80a4adde0bab73e3df64108e7ddb4b8 Mon Sep 17 00:00:00 2001
From: Petr Baudis <pasky@ucw.cz>
Date: Sun, 9 Jan 2011 16:22:06 +0100
Subject: [PATCH] Tactics nakade_point(): Simple eye-piercing tool

---
 tactics/Makefile |  2 +-
 tactics/nakade.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tactics/nakade.h | 14 ++++++++++
 3 files changed, 97 insertions(+), 1 deletion(-)
 create mode 100644 tactics/nakade.c
 create mode 100644 tactics/nakade.h

diff --git a/tactics/Makefile b/tactics/Makefile
index 82762db..344dde3 100644
--- a/tactics/Makefile
+++ b/tactics/Makefile
@@ -1,5 +1,5 @@
 INCLUDES=-I..
-OBJS=1lib.o 2lib.o nlib.o ladder.o selfatari.o util.o
+OBJS=1lib.o 2lib.o nlib.o ladder.o nakade.o selfatari.o util.o
 
 all: tactics.a
 tactics.a: $(OBJS)
diff --git a/tactics/nakade.c b/tactics/nakade.c
new file mode 100644
index 0000000..257dc49
--- /dev/null
+++ b/tactics/nakade.c
@@ -0,0 +1,82 @@
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define DEBUG
+#include "board.h"
+#include "debug.h"
+#include "move.h"
+#include "tactics/nakade.h"
+
+
+coord_t
+nakade_point(struct board *b, coord_t around, enum stone color)
+{
+	/* First, examine the nakade area. For sure, it must be at most
+	 * six points. And it must be within color group(s). */
+#define NAKADE_MAX 6
+	coord_t area[NAKADE_MAX]; int area_n = 0;
+
+	area[area_n++] = around;
+
+	for (int i = 0; i < area_n; i++) {
+		foreach_neighbor(b, area[i], {
+			if (board_at(b, c) == stone_other(color))
+				return pass;
+			if (board_at(b, c) == S_NONE) {
+				bool dup = false;
+				for (int j = 0; j < area_n; j++)
+					if (c == area[j]) {
+						dup = true;
+						break;
+					}
+				if (dup) continue;
+
+				if (area_n >= NAKADE_MAX) {
+					/* Too large nakade area. */
+					return pass;
+				}
+				area[area_n++] = c;
+			}
+		});
+	}
+
+	/* We also collect adjecency information - how many neighbors
+	 * we have for each area point, and histogram of this. This helps
+	 * us verify the appropriate bulkiness of the shape. */
+	int neighbors[area_n]; int ptbynei[9] = {area_n, 0};
+	memset(neighbors, 0, sizeof(neighbors));
+	for (int i = 0; i < area_n; i++) {
+		for (int j = i + 1; j < area_n; j++)
+			if (coord_is_adjecent(area[i], area[j], b)) {
+				ptbynei[neighbors[i]]--;
+				neighbors[i]++;
+				ptbynei[neighbors[i]]++;
+				ptbynei[neighbors[j]]--;
+				neighbors[j]++;
+				ptbynei[neighbors[j]]++;
+			}
+	}
+
+	/* For each given neighbor count, arbitrary one coordinate
+	 * featuring that. */
+	coord_t coordbynei[9];
+	for (int i = 0; i < area_n; i++)
+		coordbynei[neighbors[i]] = area[i];
+
+	switch (area_n) {
+		case 1: return pass;
+		case 2: return pass;
+		case 3: assert(ptbynei[2] == 1);
+			return coordbynei[2]; // middle point
+		case 4: if (ptbynei[3] != 1) return pass; // long line
+			return coordbynei[3]; // tetris four
+		case 5: if (ptbynei[3] == 1 && ptbynei[1] == 1) return coordbynei[3]; // bulky five
+			if (ptbynei[4] == 1) return coordbynei[4]; // cross five
+			return pass; // long line
+		case 6: if (ptbynei[4] == 1 && ptbynei[2] == 3)
+				return coordbynei[4]; // rabbity six
+			return pass; // anything else
+		default: assert(0);
+	}
+}
diff --git a/tactics/nakade.h b/tactics/nakade.h
new file mode 100644
index 0000000..0960f25
--- /dev/null
+++ b/tactics/nakade.h
@@ -0,0 +1,14 @@
+#ifndef ZZGO_TACTICS_NAKADE_H
+#define ZZGO_TACTICS_NAKADE_H
+
+/* Piercing eyes. */
+
+#include "board.h"
+#include "debug.h"
+
+/* Find an eye-piercing point within the @around area of empty board
+ * internal to group of color @color.
+ * Returns pass if the area is not a nakade shape or not internal. */
+coord_t nakade_point(struct board *b, coord_t around, enum stone color);
+
+#endif
-- 
2.11.4.GIT