1.问题

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.

Example 1:

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]

Example 2:

Input: encoded = [6,2,7,3], first = 4
Output: [4,2,0,7,4]

Constraints:

2 <= n <= 104
encoded.length == n - 1
0 <= encoded[i] <= 105
0 <= first <= 105

2. 解题思路

方法1：

1.定义一个result，长度为encoded.length+1
2.result[0]等于first
3.遍历数组，根据encoded[i] = arr[i] XOR arr[i + 1]
4.返回result

3. 代码

代码1：

class Solution {
    public int[] decode(int[] encoded, int first) {
        int[] result = new int[encoded.length+1];//1.定义一个result，长度为encoded.length+1
        result[0]= first;//2.result[0]等于first
        for (int i = 0; i < encoded.length; i++) {
    //3.遍历数组，根据encoded[i] = arr[i] XOR arr[i + 1]
                result[i+1]=encoded[i]^result[i];//解释：Java XOR 是 Java 中可用的位运算符之一。用^表示
        }
        return result;//4.返回result
    }
}