Easy O(n) HashMap based solution in C++

#1 
int Solution::solve(vector<int> &A, int B)
{
    int xr=0,count=0;
    unordered_map<int,int>m;
    for(int i=0;i<A.size();i++)
    {
        xr^=A[i];
        if(xr==B)
        {
            count++;
        }
        if(m.find(xr^B)!=m.end())
        {
            count+=m[xr^B];
        }
        m[xr]++;
    }
    return count;
}