Revert "reformulated the map coloring problem"

This reverts commit 20ab0e5.

Author: dmeoli

logic.py

@@ -741,19 +741,36 @@ def MapColoringSAT(colors, neighbors):
     if isinstance(neighbors, str):
         neighbors = parse_neighbors(neighbors)
     colors = UniversalDict(colors)
-    clauses = []
-    for state in neighbors.keys():
-        clause = [expr(state + '_' + c) for c in colors[state]]
-        clauses.append(clause)
-        for t in itertools.combinations(clause, 2):
-            clauses.append([~t[0], ~t[1]])
-        visited = set()
-        adj = set(neighbors[state]) - visited
-        visited.add(state)
-        for n_state in adj:
-            for col in colors[n_state]:
-                clauses.append([expr('~' + state + '_' + col), expr('~' + n_state + '_' + col)])
-    return associate('&', map(lambda c: associate('|', c), clauses))
+    part = str()
+    t = str()
+    for x in neighbors.keys():
+        part += '('
+        l = 0
+        for c in colors[x]:
+            l += 1
+            part += str(x) + '_' + str(c)
+            t += str(x) + '_' + str(c)
+            if l != len(colors[x]):
+                part += ' | '
+                t += '|'
+        part += ') & '
+        list = t.split('|')
+        t = str()
+        for idx, val in enumerate(list):
+            for x in list[idx + 1:]:
+                part += '~(' + val + ' & ' + x + ') & '
+    not_part = str()
+    visit = set()
+    for x in neighbors.keys():
+        adj = set(neighbors[x])
+        adj = adj - visit
+        visit.add(x)
+        for n in adj:
+            for col in colors[n]:
+                not_part += '~(' + str(x) + '_' + str(col) + ' & '
+                not_part += str(n) + '_' + str(col) + ') & '
+    clause = part + not_part[:len(not_part) - 2]
+    return expr(clause)
 
 
 australia_sat = MapColoringSAT(list('RGB'), """SA: WA NT Q NSW V; NT: WA Q; NSW: Q V; T: """)