X-Git-Url: http://git.scottworley.com/slidingtile/blobdiff_plain/b18667f24728cb960b0c60fa55824062582278bf..e0768fd268b2b06ddd08f24bfc828b397d52a1bb:/sliding_tile_lib.cc

diff --git a/sliding_tile_lib.cc b/sliding_tile_lib.cc
index 3b7806b..5b2e798 100644
--- a/sliding_tile_lib.cc
+++ b/sliding_tile_lib.cc
@@ -1,6 +1,7 @@
 #include "sliding_tile_lib.h"
 
 #include <istream>
+#include <stdexcept>
 
 signed char adjacent[BOARD_SIZE][5] = {
   1,   4,   -1,  -1,  -1,
@@ -21,7 +22,7 @@ signed char adjacent[BOARD_SIZE][5] = {
   11,  14,  -1,  -1,  -1,
 };
 
-bool Board::is_valid() {
+bool Board::is_valid() const {
   bool seen[BOARD_SIZE];
   for (int i = 0; i < BOARD_SIZE; i++) {
     seen[i] = false;
@@ -63,3 +64,12 @@ std::istream& operator>>(std::istream& is, Board& board) {
   }
   return is;
 }
+
+signed char Board::hole() const {
+  for (int i = 0; i < BOARD_SIZE; i++) {
+    if (board[i] == 0) {
+      return i;
+    }
+  }
+  throw std::runtime_error("Board with no hole");
+}