FoodDelivery: improve solution for b

Now requires truck to return to a location, also accept any location
instead of just the supply location S.

1 files changed, 15 insertions, 10 deletions

diff --git a/food_delivery/generate-food.py b/food_delivery/generate-food.py
index dc87c03..192131b 100755
--- a/food_delivery/generate-food.py
+++ b/food_delivery/generate-food.py
@@ -118,17 +118,22 @@ for j in range(1, m + 1):
     preds += ["(or %s)" % "\n".join(altpreds)]
 
 if is_b:
-    # If stock is higher or equal to initial state, then we found a loop.
+    # If any stock is higher or equal to another state in the same location,
+    # then we found a loop.
     stuff = []
-    for j in range(1, m + 1):
-        jprev = j - 1
-        highers = " ".join([
-            "(>= s{i}_{j} s{i}_0)".format(i=i, j=j)
-            for i in range(1, len(states))
-        ])
-        stuff += fillin([
-            "(and {highers})"
-        ], vars())
+    literals += ["k0", "k1"]
+    for k in range(1, m + 1):
+        for j in range(1, m + 1):
+            if k >= j:
+                continue
+            jprev = j - 1
+            highers = " ".join([
+                "(>= s{i}_{j} s{i}_{k})".format(i=i, j=j, k=k)
+                for i in range(1, len(states))
+            ])
+            stuff += fillin([
+                "(and {highers} (= l{j} l{k}) (= k0 {j}) (= k1 {k}))"
+            ], vars())
 
     preds += ["(or %s)" % " ".join(stuff)]