minor speedup

assuming the standard formulation of the 8puzzle problem, there can't be any two tiles with the same value

Author: manuel-delverme

aima-core/src/main/java/aima/core/environment/eightpuzzle/EightPuzzleBoard.java

@@ -206,18 +206,17 @@ private int getGapPosition() {
 	}
 
 	private int getPositionOf(int val) {
-		int retVal = -1;
 		for (int i = 0; i < 9; i++) {
 			if (state[i] == val) {
-				retVal = i;
+				return i
 			}
 		}
-		return retVal;
+		return -1;
 	}
 
 	private void setValue(int x, int y, int val) {
 		int absPos = getAbsPosition(x, y);
 		state[absPos] = val;
 
 	}
-}
+}