Find Palindrome With Fixed Length LeetCode solution in C++

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#define ll long long
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class Solution {
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 public:
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  vector<long long> kthPalindrome(vector<int> &queries, int intLength) {
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    vector<ll> result;
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    ll start = intLength % 2 == 0 ? pow(10, intLength / 2 - 1) : pow(10, intLength / 2);
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    for (int q : queries) {
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      string s = to_string(start + q - 1);
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      string palindrome = s;
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      reverse(s.begin(), s.end());
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      if (intLength % 2 == 0) {
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        palindrome += s;
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      } else {
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        palindrome += s.substr(1, s.size() - 1);
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      }
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      // len of palindrome should be intLength, otherwise -1
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      if (palindrome.size() == intLength)
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        result.push_back(stoll(palindrome));
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      else
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        result.push_back(-1);
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    }
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    return result;
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  }
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};