Decode XORed Permutation LeetCode solution in C++

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class Solution {
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 public:
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  vector<int> decode(vector<int> &encoded) {
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    int n = encoded.size(), x = 0;
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    // XOR of the permutation
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    for (int i = 1; i <= n + 1; i++) x ^= i;
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    // Xoring X with all the odd positioned elements to find first number
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    for (int i = 1; i < n; i += 2) x ^= encoded[i];
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    vector<int> res;
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    res.push_back(x);
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    for (int i = 0; i < n; i++) {
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      x ^= encoded[i];
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      res.push_back(x);
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    }
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    return res;
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  }
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};