'''
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
'''
from typing import *

import unittest


class Solution:
    def xorQueries(self, arr: List[int], queries: List[List[int]]) -> List[int]:
        pre = [0 for _ in range(len(arr))]
        
        for i in range(len(arr)):
            if i == 0:
                pre[i] = arr[i]
            else:
                pre[i] = pre[i - 1] ^ arr[i]
        
        res = []
        for left, right in queries:
            if left == 0:
                res.append(pre[right])
            else:
                res.append(pre[left - 1] ^ pre[right])
        return res


class TestSolution(unittest.TestCase):

    def test_case(self):
        examples = (
            (([1,3,4,8], [[0,1],[1,2],[0,3],[3,3]]), [2,7,14,8]),
            (([4,8,2,10], [[2,3],[1,3],[0,0],[0,3]]), [8,0,4,4])
        )
        for first, second in examples:
            self.assert_function(first, second)

    def assert_function(self, first, second):
        self.assertEqual(Solution().xorQueries(*first), second,
                         msg="first: {}; second: {}".format(first, second))


unittest.main()
