decode-xored-permutation

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1734. Decode XORed Permutation (Medium)

There is an integer array perm that is a permutation of the first n positive integers, where n is always odd.

It was encoded into another integer array encoded of length n - 1, such that encoded[i] = perm[i] XOR perm[i + 1]. For example, if perm = [1,3,2], then encoded = [2,1].

Given the encoded array, return the original array perm. It is guaranteed that the answer exists and is unique.

 

Example 1:

Input: encoded = [3,1]
Output: [1,2,3]
Explanation: If perm = [1,2,3], then encoded = [1 XOR 2,2 XOR 3] = [3,1]

Example 2:

Input: encoded = [6,5,4,6]
Output: [2,4,1,5,3]

 

Constraints:

• 3 <= n < 105
• n is odd.
• encoded.length == n - 1

Related Topics

[Array] [Bit Manipulation]

Hints

Hint 1

Compute the XOR of the numbers between 1 and n, and think about how it can be used. Let it be x.

Hint 2

Think why n is odd.

Hint 3

perm[0] = x XOR encoded[1] XOR encoded[3] XOR encoded[5] ...

Hint 4

perm[i] = perm[i-1] XOR encoded[i-1]