84 lines
2.0 KiB
Python
84 lines
2.0 KiB
Python
"""
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name: Nicholas Tamassia
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Honor Code and Acknowledgments:
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This work complies with the JMU Honor Code.
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Comments here on your code and submission.
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"""
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import math
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from collections import defaultdict
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def find_arbitrage(graph: dict[str, dict[str, float]]) -> list[str] | None:
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weights: dict[str, float] = {c: math.inf for c in graph}
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prev: dict[str, str | None] = {c: None for c in graph}
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start: str = list(graph.keys())[0]
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weights[start] = 0
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for _ in range(len(graph) - 1):
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for src in graph:
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for dest, rate in graph[src].items():
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weight: float = -math.log(rate)
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if weights[src] + weight < weights[dest]:
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weights[dest] = weights[src] + weight
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prev[dest] = src
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node: str | None = None
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for src in graph:
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for dest, rate in graph[src].items():
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weight: float = -math.log(rate)
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if weights[src] + weight < weights[dest]:
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node = dest
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prev[dest] = src
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break
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if node is not None:
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break
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if node is None:
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return
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for _ in range(len(graph)):
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node = prev[node]
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path = [node]
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while True:
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node = prev[node]
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path.append(node)
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if node == path[0]:
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break
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path.reverse()
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return path
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def main():
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n: int = int(input().strip())
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graph: dict[str, dict[str, float]] = defaultdict(dict)
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for _ in range(n):
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vals: list[str] = input().strip().split()
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src: str = vals[0]
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dest: str = vals[1]
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rate: float = float(vals[2])
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graph[src][dest] = rate
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path = find_arbitrage(graph)
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if path is not None:
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print("Arbitrage Detected")
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print(" => ".join(path))
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factor = 1.0
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for i in range(len(path) - 1):
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factor *= graph[path[i]][path[i + 1]]
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print(f"{factor:.5f} factor increase")
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else:
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print("No Arbitrage Detected")
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if __name__ == "__main__":
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main()
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