This is regarding the Chef and Xor queries problem which came in Dec challenge. I am getting TLE in two test cases of last test cases. Link to the solution. I have used square root decomposition and tried to lazily make the updates as and when required. But no luck yet.
The timeout was caused by the use of operator when fetching the map value.
When you try to access a mapped value through operator, it allocates the element (i.e. mapped value for searched key) if not already present. So, it allocates unnecessary elements in the map, resulting in slower search operation.
I got your solution accepted for 100 points by checking if the key is allocated a value in the map or not, before accessing the map through this condition :
if(dp[i].find(xorNeed) != dp[i].end())
Edited code :
 : https://www.codechef.com/viewsolution/16576761