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https://github.com/onyx-and-iris/grokking-algorithms.git
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74 lines
1.5 KiB
Python
74 lines
1.5 KiB
Python
import logging
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import math
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logging.basicConfig(level=logging.DEBUG)
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logger = logging.getLogger(__name__)
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graph = {}
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graph["start"] = {}
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graph["start"]["a"] = 5
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graph["start"]["b"] = 2
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graph["a"] = {}
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graph["a"]["b"] = 8
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graph["a"]["c"] = 4
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graph["a"]["d"] = 2
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graph["b"] = {}
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graph["b"]["a"] = 8
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graph["b"]["d"] = 7
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graph["c"] = {}
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graph["c"]["d"] = 6
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graph["c"]["fin"] = 3
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graph["d"] = {}
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graph["d"]["fin"] = 1
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graph["fin"] = {}
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costs = {}
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costs["a"] = 5
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costs["b"] = 2
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costs["c"] = math.inf
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costs["d"] = math.inf
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costs["fin"] = math.inf
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parents = {}
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parents["a"] = "start"
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parents["b"] = "start"
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parents["c"] = None
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parents["d"] = None
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parents["fin"] = None
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processed = set()
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def find_lowest_cost_node(costs):
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lowest_cost = math.inf
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lowest_cost_node = None
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for node in costs:
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cost = costs[node]
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if cost < lowest_cost and node not in processed:
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lowest_cost = cost
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lowest_cost_node = node
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return lowest_cost_node
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node = find_lowest_cost_node(costs)
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while node is not None:
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cost = costs[node]
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neighbors = graph[node]
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for n in neighbors.keys():
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new_cost = cost + neighbors[n]
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if costs[n] > new_cost:
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costs[n] = new_cost
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parents[n] = node
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processed.add(node)
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node = find_lowest_cost_node(costs)
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print(f"lowest cost route: {costs['fin']}")
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route = []
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next = "fin"
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while next != "start":
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route.append(next)
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next = parents[next]
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route.append("start")
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print(f"route: {list(reversed(route))}")
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