1734. Decode XORed Permutation 

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class Solution {
    public int[] decode(int[] encoded) {
        int[] res = new int[encoded.length + 1];

        int tmp = 0;
        for (int i = 0; i < encoded.length; i += 2) {
            tmp ^= encoded[i];
        }

        int last = tmp;
        for (int num = 1; num <= encoded.length + 1; num++) {
            last ^= num;
        }
        res[res.length - 1] = last;
        for (int i = res.length - 2; i >= 0; i--) {
            res[i] = res[i + 1] ^ encoded[i];
        }

        return res;
    }
}

References

1734. Decode XORed Permutation