1
class Solution:
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    def numSpecial(self, mat: List[List[int]]) -> int:
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        def get_column_sum(col_idx):
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            return sum(row[col_idx] for row in mat)
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        special = 0
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        for row in mat:
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            if sum(row) == 1:
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                col_idx = row.index(1)
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                special += get_column_sum(col_idx) == 1
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        return special