Problem link: CHEFEXQ
Given an array of n elements and q queries of 2 types:
type 1: Given two numbers p and x, the value at index p should be updated to x.
type 2: Given two numbers p and x, calculate total number of subarrays whose starting index is 0 and the last index is ≤ p and the xor of all elements in that subarray is equal to x.
This problem can be solved using square root decomposition technique. I have wrote an editorial of this problem on my blog.