1734. Decode XORed Permutation

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

Rust Solution

struct Solution;

impl Solution {
    fn decode(encoded: Vec<i32>) -> Vec<i32> {
        let n = encoded.len() + 1;
        let mut first = 0;
        for i in 0..n {
            first ^= (i + 1) as i32;
        }
        for i in 0..n - 1 {
            if i % 2 == 1 {
                first ^= encoded[i];
            }
        }
        let mut res = vec![first];
        for i in 1..n {
            res.push(res[i - 1] ^ encoded[i - 1]);
        }
        res
    }
}

#[test]
fn test() {
    let encoded = vec![3, 1];
    let res = vec![1, 2, 3];
    assert_eq!(Solution::decode(encoded), res);
    let encoded = vec![6, 5, 4, 6];
    let res = vec![2, 4, 1, 5, 3];
    assert_eq!(Solution::decode(encoded), res);
}

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