Decode XORed Permutation LeetCode solution in Java

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class Solution {
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  public int[] decode(int[] encoded) {
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    int n = encoded.length + 1, all = 0;
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    for (int i = 1; i <= n; ++i) { // a^b^c^d^e^f^g^h^i
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      all ^= i;
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    }
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    int x = 0;
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    for (int v : encoded) { // a^b  b^c  c^d  d^e e^f f^g g^h h^i = a^i
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      x ^= v;
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    }
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    int mid = all ^ x; // a^b^c^d^e^f^g^h^i ^ a^i = b^c^d^e^f^g^h
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    for (int i = 1, j = encoded.length - 2; i < j; i += 2, j -= 2) {
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      // (b^c^d^e^f^g^h) ^ (b^c ^ g^h ^ d^e ^ e^f) = e
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      mid ^= encoded[i] ^ encoded[j];
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    }
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    int[] ans = new int[n];
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    ans[n / 2] = mid;
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    // a    b    c    d   e   f   g   h   i
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    // a^b  b^c  c^d  d^e e^f f^g g^h h^i
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    for (int i = n / 2 + 1; i < n; ++i) {
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      ans[i] = encoded[i - 1] ^ ans[i - 1];
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    }
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    for (int i = n / 2 - 1; i >= 0; --i) {
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      ans[i] = encoded[i] ^ ans[i + 1];
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    }
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    return ans;
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  }
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}