//There is a list of list for int data //each sub list of main list is sorted within itself (refer subList1 to subList4) // entry of first element in each list of sub list is sorted (refer subList1[0] using namespace std; #include void printSortedData(list> mainList) { list sortedList; // collect all data in a single list for(auto itr1 = mainList.begin();itr1!=mainList.end();++itr1) { list tmpList = *itr1; for(auto itr2 = tmpList.begin();itr2!=tmpList.end();++itr2) { sortedList.push_back(*itr2); } } //sort data sortedList.sort(); //print data for(auto itr = sortedList.begin();itr!=sortedList.end();++itr) { cout << *itr << ","; } } void printSortedData_Optimized(list> mainList) { list sortedList = {}; // collect all data in a single list for(auto itr1 = mainList.begin();itr1!=mainList.end();++itr1) { sortedList.merge(*itr1); } //print data for(auto itr = sortedList.begin();itr!=sortedList.end();++itr) { cout << *itr << ","; } } int main() { list subList1 = {1,10,20,30}; list subList2 = {5,7,9}; list subList3 = {12,19,39,48}; list subList4 = {15,22,28,33}; list> mainList; mainList.push_back(subList1); mainList.push_back(subList2); mainList.push_back(subList3); mainList.push_back(subList4); printSortedData_Optimized(mainList); return 0; }

SortListofList