Compilare: user.cpp: In function ‘void compute()’: user.cpp:38:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < formula[i - 1].size(); ++j) ^ user.cpp:41:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < formula[i - 1].size() - 1; ++j) ^ user.cpp:42:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int t = 0; t < formula[j].size(); ++t) ^ user.cpp:45:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < formula[i - 1].size(); ++j) ^ user.cpp:48:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < formula[i].size(); ++j) ^ user.cpp: In function ‘int main()’: user.cpp:56:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < formula[k].size(); ++i) ^