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Task/Topological-sort/Python/topological-sort.py

@@ -0,0 +1,36 @@
+try:
+    from functools import reduce
+except:
+    pass
+
+data = {
+    'des_system_lib':   set('std synopsys std_cell_lib des_system_lib dw02 dw01 ramlib ieee'.split()),
+    'dw01':             set('ieee dw01 dware gtech'.split()),
+    'dw02':             set('ieee dw02 dware'.split()),
+    'dw03':             set('std synopsys dware dw03 dw02 dw01 ieee gtech'.split()),
+    'dw04':             set('dw04 ieee dw01 dware gtech'.split()),
+    'dw05':             set('dw05 ieee dware'.split()),
+    'dw06':             set('dw06 ieee dware'.split()),
+    'dw07':             set('ieee dware'.split()),
+    'dware':            set('ieee dware'.split()),
+    'gtech':            set('ieee gtech'.split()),
+    'ramlib':           set('std ieee'.split()),
+    'std_cell_lib':     set('ieee std_cell_lib'.split()),
+    'synopsys':         set(),
+    }
+
+def toposort2(data):
+    for k, v in data.items():
+        v.discard(k) # Ignore self dependencies
+    extra_items_in_deps = reduce(set.union, data.values()) - set(data.keys())
+    data.update({item:set() for item in extra_items_in_deps})
+    while True:
+        ordered = set(item for item,dep in data.items() if not dep)
+        if not ordered:
+            break
+        yield ' '.join(sorted(ordered))
+        data = {item: (dep - ordered) for item,dep in data.items()
+                if item not in ordered}
+    assert not data, "A cyclic dependency exists amongst %r" % data
+
+print ('\n'.join( toposort2(data) ))