adds chapter9 exercises with heap and without

chapter9/with_list_function/ex171a.py

@@ -0,0 +1,71 @@
+import logging
+import math
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+graph = {
+    "start": {"a": 5, "b": 2},
+    "a": {"b": 8, "c": 4, "d": 2},
+    "b": {"a": 8, "d": 7},
+    "c": {"d": 6, "fin": 3},
+    "d": {"fin": 1},
+    "fin": {},
+}
+
+costs = {
+    "a": 5,
+    "b": 2,
+    "c": math.inf,
+    "d": math.inf,
+    "fin": math.inf,
+}
+
+parents = {
+    "a": "start",
+    "b": "start",
+    "c": None,
+    "d": None,
+    "fin": None,
+}
+
+processed = set()
+
+
+def find_lowest_cost_node(costs):
+    lowest_cost = math.inf
+    lowest_cost_node = None
+    for node in costs:
+        cost = costs[node]
+        if cost < lowest_cost and node not in processed:
+            lowest_cost = cost
+            lowest_cost_node = node
+    return lowest_cost_node
+
+
+node = find_lowest_cost_node(costs)
+while node is not None:
+    cost = costs[node]
+    neighbors = graph[node]
+    for n in neighbors.keys():
+        new_cost = cost + neighbors[n]
+        if costs[n] > new_cost:
+            costs[n] = new_cost
+            parents[n] = node
+    processed.add(node)
+    node = find_lowest_cost_node(costs)
+
+print(f"lowest cost route: {costs['fin']}")
+
+
+def get_full_route():
+    route = []
+    next = "fin"
+    while next != "start":
+        route.append(next)
+        next = parents[next]
+    route.append("start")
+    return list(reversed(route))
+
+
+print(f"route: {get_full_route()}")

chapter9/with_list_function/ex171b.py

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+import logging
+import math
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+graph = {
+    "start": {"a": 10},
+    "a": {"c": 20},
+    "b": {"a": 1, "c": 1},
+    "c": {"b": 1, "fin": 30},
+    "fin": {},
+}
+
+costs = {
+    "a": 10,
+    "b": math.inf,
+    "c": math.inf,
+    "fin": math.inf,
+}
+
+parents = {
+    "a": "start",
+    "b": None,
+    "c": None,
+    "fin": None,
+}
+
+processed = set()
+
+
+def find_lowest_cost_node(costs):
+    lowest_cost = math.inf
+    lowest_cost_node = None
+    for node in costs:
+        cost = costs[node]
+        if cost < lowest_cost and node not in processed:
+            lowest_cost = cost
+            lowest_cost_node = node
+    return lowest_cost_node
+
+
+node = find_lowest_cost_node(costs)
+while node is not None:
+    cost = costs[node]
+    neighbors = graph[node]
+    for n in neighbors.keys():
+        new_cost = cost + neighbors[n]
+        if costs[n] > new_cost:
+            costs[n] = new_cost
+            parents[n] = node
+    processed.add(node)
+    node = find_lowest_cost_node(costs)
+
+print(f"lowest cost route: {costs['fin']}")

chapter9/with_list_function/ex171c.py

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+import logging
+import math
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+graph = {
+    "start": {"a": 2, "b": 2},
+    "a": {"b": 2},
+    "b": {"c": 2, "fin": 2},
+    "c": {"fin": 2},
+    "fin": {},
+}
+
+
+costs = {
+    "a": 2,
+    "b": 2,
+    "c": math.inf,
+    "fin": math.inf,
+}
+
+parents = {
+    "a": "start",
+    "b": "start",
+    "c": None,
+    "fin": None,
+}
+
+processed = set()
+
+
+def find_lowest_cost_node(costs):
+    lowest_cost = math.inf
+    lowest_cost_node = None
+    for node in costs:
+        cost = costs[node]
+        if cost < lowest_cost and node not in processed:
+            lowest_cost = cost
+            lowest_cost_node = node
+    return lowest_cost_node
+
+
+node = find_lowest_cost_node(costs)
+while node is not None:
+    cost = costs[node]
+    neighbors = graph[node]
+    for n in neighbors.keys():
+        new_cost = cost + neighbors[n]
+        if costs[n] > new_cost:
+            costs[n] = new_cost
+            parents[n] = node
+    processed.add(node)
+    node = find_lowest_cost_node(costs)
+
+print(f"lowest cost route: {costs['fin']}")