1720. Decode XORed Array

Easy

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

解題

利用 XOR 的性質來解題， a ^ b = c，則 a ^ c = b。

func decode(encoded []int, first int) []int {
    res := make([]int, 0)
    res = append(res, first)
    res = append(res, encoded...)
    
    for i:=1; i<len(res); i++ {
        res[i] = res[i] ^ res[i-1]
    }
    
    return res
}