Decode XOR Array
A hidden array was encoded by XORing each adjacent pair: `encoded[i] = arr[i] ^ arr[i + 1]`. Given the encoded array and the value of the first element, reconstruct and return the original array.
A hidden array was encoded by XORing each adjacent pair: `encoded[i] = arr[i] ^ arr[i + 1]`. Given the encoded array and the value of the first element, reconstruct and return the original array.