Dungeon Game LeetCode solution in Python

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class Solution:
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    def calculateMinimumHP(self, dungeon: List[List[int]]) -> int:
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        dp = defaultdict(lambda: inf)
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        dp[(len(dungeon), len(dungeon[0]) - 1)] = 1
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        for i in range(len(dungeon) - 1, -1, -1):
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            for j in range(len(dungeon[0]) - 1, -1, -1):
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                dp[(i, j)] = min(dp[(i + 1, j)], dp[(i, j + 1)]) - dungeon[i][j]
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                if dp[(i, j)] <= 0:
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                    dp[(i, j)] = 1
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        return dp[(0, 0)]