1
var canThreePartsEqualSum = function (arr) {
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  const length = arr.length;
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  let sum = 0,
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    count = 0,
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    partSum = 0;
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  for (let index = 0; index < length; index++) {
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    sum += arr[index];
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  }
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  if (sum % 3 !== 0) return false;
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  partSum = sum / 3;
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  sum = 0;
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  for (let index = 0; index < length; index++) {
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    sum += arr[index];
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    if (sum === partSum) {
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      count++;
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      sum = 0;
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      if (count == 2 && index < length - 1) return true;
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    }
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  }
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  return false;
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};