LeetCode-in-Java
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 < 105nis odd.encoded.length == n - 1
Solution
public class Solution {
public int[] decode(int[] encoded) {
int[] decoded = new int[encoded.length + 1];
for (int i = 1; i < encoded.length; i = i + 2) {
decoded[0] = decoded[0] ^ encoded[i];
decoded[0] = decoded[0] ^ i;
decoded[0] = decoded[0] ^ i + 1;
}
decoded[0] = decoded[0] ^ decoded.length;
for (int i = 1; i < decoded.length; i++) {
decoded[i] = decoded[i - 1] ^ encoded[i - 1];
}
return decoded;
}
}