g1701_1800.s1720_decode_xored_array.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g1701_1800.s1720_decode_xored_array;

// #Easy #Array #Bit_Manipulation #2022_04_24_Time_1_ms_(100.00%)_Space_57.3_MB_(6.33%)

/**
 * 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
**/
public class Solution {
    public int[] decode(int[] encoded, int first) {
        int[] arr = new int[encoded.length + 1];
        arr[0] = first;
        for (int i = 0; i < encoded.length; i++) {
            arr[i + 1] = encoded[i] ^ arr[i];
        }
        return arr;
    }
}