Compilare: user.cpp: In function ‘void push(int)’: user.cpp:29:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < tab[h].size(); ++i) { ^ user.cpp: In function ‘void pop(int)’: user.cpp:42:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < tab[h].size(); ++i) { ^ user.cpp: In function ‘bool check(int)’: user.cpp:53:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < tab[h].size(); ++i) { ^