Formatted question description: https://leetcode.ca/all/1720.html
1720. Decode XORed Array
Level
Easy
Description
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 <= 10^4encoded.length == n - 10 <= encoded[i] <= 10^50 <= first <= 10^5
Solution
Create an array arr of length n + 1 and set arr[0] = first. Then use the property of XOR such that if a ^ b == c then there is a ^ c == b and b ^ c == a. Therefore, for each i from 0 to n - 1, there is arr[i + 1] = arr[i] ^ encoded[i]. Finally, return arr.
class Solution {
public int[] decode(int[] encoded, int first) {
int length = encoded.length;
int[] arr = new int[length + 1];
arr[0] = first;
for (int i = 0; i < length; i++)
arr[i + 1] = arr[i] ^ encoded[i];
return arr;
}
}