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var isPerfectSquare = function (num) {
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  let low = 1;
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  let high = 100000;
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  while (low <= high) {
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    let mid = (low + high) >> 1;
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    let sqrt = mid * mid;
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    if (sqrt == num) {
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      return true;
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    } else if (num > sqrt) {
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      low = mid + 1;
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    } else {
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      high = mid - 1;
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    }
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  }
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  return false;
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};