add greedy

chapter10/greedy.py

@@ -0,0 +1,44 @@
+import logging
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+stations = {
+    "kone": set(["id", "nv", "ut"]),
+    "ktwo": set(["wa", "id", "mt"]),
+    "kthree": set(["or", "nv", "ca"]),
+    "kfour": set(["nv", "ut"]),
+    "kfive": set(["ca", "az"]),
+}
+
+
+def greedy():
+    def fget():
+        needed = set()
+        for states in stations.values():
+            needed |= states
+        return needed
+
+    states_needed = fget()
+    logger.debug(states_needed)
+
+    final_stations = set()
+
+    while states_needed:
+        best_station = None
+        states_covered = set()
+        for station, states in stations.items():
+            covered = states_needed & states
+
+            if len(covered) > len(states_covered):
+                best_station = station
+                states_covered = covered
+
+        states_needed -= states_covered
+        final_stations.add(best_station)
+
+    return final_stations
+
+
+final_stations = greedy()
+print(f"final stations greedy approximation: {final_stations}")