Recursive counting.. classSolution {longlongw(intn) {longlongret =1;while(n >1) { ret*=n; n--; }returnret; }longlongcalc(vector<int>& A,inti,longlongpwr,intlast) {if(last ==0)return0;intd = A[i] -1;longlongcurr = d *pwr;for(intj = i +1; j < A.size(); j ++) ...