Optimise applyCW

1 files changed, 27 insertions, 3 deletions

diff --git a/board.cpp b/board.cpp
index 04f0c70..b49b077 100644
--- a/board.cpp
+++ b/board.cpp
@@ -141,9 +141,33 @@ void Board::apply(Move mv) {
 }
 
 int Board::applyCW(Move mv) {
-	// TODO: make more efficient
-	apply(mv);
-	return checkWin();
+	int x2 = mv.to % N, y2 = mv.to / N;
+
+	if (cells[mv.from] == KING) {
+		apply(mv);
+
+		if (cells[mv.to] == KING) {
+			if (x2 == 0 || x2 == N-1 || y2 == 0 || y2 == N-1) return 1;
+		}
+	} else {
+		bool haveking1 =
+				(x2 > 0 && cells[mv.to - 1] == KING) ||
+				(y2 > 0 && cells[mv.to - N] == KING) ||
+				(x2 < N-1 && cells[mv.to + 1] == KING) ||
+				(y2 < N-1 && cells[mv.to + N] == KING);
+
+		apply(mv);
+
+		bool haveking2 =
+				(x2 > 0 && cells[mv.to - 1] == KING) ||
+				(y2 > 0 && cells[mv.to - N] == KING) ||
+				(x2 < N-1 && cells[mv.to + 1] == KING) ||
+				(y2 < N-1 && cells[mv.to + N] == KING);
+
+		if (haveking1 && !haveking2) return -1;
+	}
+
+	return 0;
 }
 
 int Board::checkWin() const {