Continuous Subarray Sum LeetCode solution in C++

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class Solution {
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 public:
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  bool checkSubarraySum(vector<int> &nums, int k) {
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    unordered_set<int> s;
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    int sum = 0;
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    int pre = 0;
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    for (int i = 0; i < nums.size(); i++) {
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      sum += nums[i];
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      int remainder = sum % k;
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      if (s.find(remainder) != s.end()) {
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        return true;
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      }
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      s.insert(pre);
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      pre = remainder;
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    }
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    return false;
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  }