Compilare: main.cpp: In function 'int main()': main.cpp:25:60: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while((!S.empty()) && cif>S.top() && S.size()+(n-i)>=k) S.pop(); ~~~~~~~~~~~~~~^~~ main.cpp:29:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(S.size()!=k) ~~~~~~~~^~~ main.cpp:38:14: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] numar[ct]=NULL; ^~~~