decodeAnArray.java

/*1720. Decode XORed Array
 * There is a hidden integer array arr that consists of n non-negative integers.It was encoded into another integer array encoded of length n - 1, such that encoded[i] = arr[i] XOR arr[i + 1]. For example, if arr = [1,0,2,1], then encoded = [1,2,3].
 You are given the encoded array. You are also given an integer first, that is the first element of arr, i.e. arr[0].
 Return the original array arr. It can be proved that the answer exists and is unique.
 *
 * Input: encoded = [1,2,3], first = 1
 * Output: [1,0,2,1]
 * Explanation: If arr = [1,0,2,1], then first = 1 and encoded = [1 XOR 0, 0 XOR 2, 2 XOR 1] = [1,2,3]
 */

public class decodeAnArray {
    public static int[] decode(int[] encoded, int first){
        int[] decoded = new int[encoded.length + 1];
        int index = 0;
        decoded[index++] = first;

        for(int i=0; i<encoded.length; i++){
            decoded[index++] = encoded[i] ^ decoded[i];
        }
        return decoded;
    }

    public static void main(String[] args) {
        int[] encoded = {1,2,3};
        int first = 1;
        int[] resultArr = decode(encoded, first);
        for(int element : resultArr){
            System.out.print(element + " ");
        }
    }
}

/*Note: ^ operator in java is XOR operator. 
Inverse of XOR, is XOR itself.
*/