Compilare: main.cpp: In function 'int main()': main.cpp:20:20: warning: array subscript has type 'char' [-Wchar-subscripts] S[s2[i]].insert(i); ^ main.cpp:25:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s1.size();i++){ ~^~~~~~~~~~ main.cpp:31:34: warning: array subscript has type 'char' [-Wchar-subscripts] auto it = S[s1[j]].upper_bound(j); ^ main.cpp:32:34: warning: array subscript has type 'char' [-Wchar-subscripts] if (it == S[s1[j]].end()) break; ^ main.cpp:41:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=1;i<ans.back().size();i++){ ~^~~~~~~~~~~~~~~~~~ main.cpp:43:25: warning: array subscript has type 'char' [-Wchar-subscripts] S[s2[it]].erase(it); ^