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​​

题解：

class Solution {
public:
    vector<int> xorQueries(vector<int>& arr, vector<vector<int>>& queries) {
        int n = arr.size();
        vector<int> pre(n + 1, 0);
        vector<int> res;
        for (int i = 0; i < n; i++) {
            pre[i + 1] = arr[i] ^ pre[i];
        }
        for (int i = 0; i < queries.size(); i++)  {
            int tmp = pre[queries[i][0]] ^ pre[queries[i][1] + 1];
            res.push_back(tmp);
        }
        return res;
    }
};