From 2b84767d5b493bde658b443637b8733cfaf57a34 Mon Sep 17 00:00:00 2001
From: Peter Wu <peter@lekensteyn.nl>
Date: Fri, 13 Jan 2017 18:18:51 +0100
Subject: FoodDelivery: improve solution for b

Now requires truck to return to a location, also accept any location
instead of just the supply location S.
---
 food_delivery/food-to-table.py | 11 ++++++++---
 food_delivery/generate-food.py | 25 +++++++++++++++----------
 2 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/food_delivery/food-to-table.py b/food_delivery/food-to-table.py
index b94ad0c..c66a774 100755
--- a/food_delivery/food-to-table.py
+++ b/food_delivery/food-to-table.py
@@ -7,6 +7,8 @@ n = 5
 
 matrix = []
 nextNodes = {}
+# The pair that shows a loop (for b)
+pair_for_b = [None] * 2
 
 for line in sys.stdin:
     line = line.strip()
@@ -23,6 +25,10 @@ for line in sys.stdin:
             matrix.append([None] * n)
 
         matrix[step][villagenr] = value
+    elif line.startswith('k'):
+        m = re.match(r'k(\d+) -> (\d+)', line)
+        step, value = map(int, m.groups())
+        pair_for_b[step] = value
     else:
         m = re.match(r'l(\d+) -> (\d+)', line)
         step, value = map(int, m.groups())
@@ -45,8 +51,7 @@ for step, cells in enumerate(matrix):
         else:
             line += " & %5d" % value
     line += r" & %s \\" % "SABCD"[nextNodes[step]]
-    if step > 0:
-        if all(x >= y for x, y in zip(matrix[step][1:], matrix[0][1:])):
-            line += " % HIGHER"
+    if any(x == step for x in pair_for_b):
+        line += " % PAIR"
     #line += r" \\"
     print(line)
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)]
 
-- 
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