Compilare: main.cpp: In function 'bool check(int)': main.cpp:38:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j < sol.size(); j++) { ~~^~~~~~~~~~~~ main.cpp: In function 'void solve()': main.cpp:59:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (check(i) && sol.size() == ni) { ~~~~~~~~~~~^~~~~ main.cpp:62:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < sol.size(); i++) ~~^~~~~~~~~~~~