Compilare: main.cpp: In function 'void push(int)': main.cpp:14:9: warning: unused variable 'i' [-Wunused-variable] int x, i; ^ main.cpp: In function 'bool ask(int)': main.cpp:34:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < H[x].size(); ++ i) ~~^~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:41:6: warning: unused variable 'i' [-Wunused-variable] int i, tip, val; ^