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class Solution {
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 public:
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  bool canThreePartsEqualSum(vector<int> &arr) {
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    int sum = 0;
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    for (auto i : arr) sum += i;
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    if (sum % 3 != 0) return false; // partition not possible
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    int part = sum / 3, temp = 0, found = 0;
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    for (int i = 0; i < arr.size(); i++) {
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      temp += arr[i];
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      if (temp == part) {
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        temp = 0;
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        found++;
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      }
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    }
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    return found >= 3 ? true : false;
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  }
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};
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feel free to ask your doubts :)
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and pls upvote if it was helpful :)