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# Runtime: 668 ms (Top 23.61%) | Memory: 21 MB (Top 37.82%)
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class Solution:
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    def canThreePartsEqualSum(self, arr: List[int]) -> bool:
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        total = sum(arr)
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        if total % 3 != 0:
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            return False
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        ave = total // 3
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        stage = 0
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        add = 0
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        for i in arr[:-1]:
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            add += i
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            if add == ave:
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                stage += 1
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                add = 0
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            if stage == 2:
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                return True
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        return False