diff --git a/src/util.py b/src/util.py
--- a/src/util.py
+++ b/src/util.py
@@ -52,6 +52,9 @@ def hashBoard(board):
 			res^=zobristNums[r][c][item+1]
 	return res
 
+def diffHash(r,c,oldItem,newItem):
+	h=zobristNums[r][c]
+	return h[oldItem+1] ^ h[newItem+1]
 
 def exportBoard(board):
 	substitutions={EMPTY:".", BLACK:"X", WHITE:"O"}