No1310.XOR-queries-of-a-subarray.cs

/*
 * Difficulty:
 * Medium
 *
 * Desc:
 * Given the array arr of positive integers and the array queries where queries[i] = [Li, Ri],
 * for each query i compute the XOR of elements from Li to Ri (that is, arr[Li] xor arr[Li+1] xor ... xor arr[Ri] ).
 * Return an array containing the result for the given queries.
 *
 * Example 1:
 * Input: arr = [1,3,4,8], queries = [[0,1],[1,2],[0,3],[3,3]]
 * Output: [2,7,14,8] 
 * Explanation: 
 * The binary representation of the elements in the array are:
 * 1 = 0001 
 * 3 = 0011 
 * 4 = 0100 
 * 8 = 1000 
 * The XOR values for queries are:
 * [0,1] = 1 xor 3 = 2 
 * [1,2] = 3 xor 4 = 7 
 * [0,3] = 1 xor 3 xor 4 xor 8 = 14 
 * [3,3] = 8
 *
 * Example 2:
 * Input: arr = [4,8,2,10], queries = [[2,3],[1,3],[0,0],[0,3]]
 * Output: [8,0,4,4]
 *
 * Constraints:
 * 1 <= arr.length <= 3 * 10^4
 * 1 <= arr[i] <= 10^9
 * 1 <= queries.length <= 3 * 10^4
 * queries[i].length == 2
 * 0 <= queries[i][0] <= queries[i][1] < arr.length
*/

public class Solution {
    public int[] XorQueries(int[] arr, int[][] queries) {
        int[] prefix = new int[arr.Length + 1];
        prefix[0] = 1;

        for (int i = 0; i < arr.Length; i += 1) {
            prefix[i + 1] = prefix[i] ^ arr[i];
        }
        
        return queries.Select((int[] query) => prefix[query[1] + 1] ^ prefix[query[0]]).ToArray();
    }
}