Compilare: main.cpp: In function 'void add(int)': main.cpp:39:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a[key].size(); ++i) { ~~^~~~~~~~~~~~~~~ main.cpp: In function 'void eraseElement(int)': main.cpp:58:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a[key].size(); ++i) { ~~^~~~~~~~~~~~~~~ main.cpp:56:10: warning: variable 'found' set but not used [-Wunused-but-set-variable] bool found = false; ^~~~~ main.cpp: In function 'int isElement(int)': main.cpp:73:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a[key].size() && found == 0; ++i) { ~~^~~~~~~~~~~~~~~