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1310. XOR Queries of a Subarray

Difficulty Topics

Description

You are given an array arr of positive integers. You are also given the array queries where queries[i] = [lefti, righti].

For each query i compute the XOR of elements from lefti to righti (that is, arr[lefti] XOR arr[lefti + 1] XOR ... XOR arr[righti] ).

Return an array answer where answer[i] is the answer to the ith query.

 

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, queries.length <= 3 * 104
  • 1 <= arr[i] <= 109
  • queries[i].length == 2
  • 0 <= lefti <= righti < arr.length

Solution

xor-queries-of-a-subarray.py
class Solution:
    def xorQueries(self, arr: List[int], queries: List[List[int]]) -> List[int]:
        res = []
        prefix = [0]
        for x in arr:
            prefix.append(x ^ prefix[-1])

        for l,r in queries:
            res.append(prefix[l] ^ prefix[r+1])

        return res