Compilare: user.cpp: In function ‘bool isValid(std::vector<int>&, unsigned int)’: user.cpp:26:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (stack[stack.size() - 1] >= size) return false; user.cpp: In function ‘int main()’: user.cpp:58:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (unsigned j = 0; j < m; j++) { ~~^~~ user.cpp:95:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (unsigned j = 0; j < m; j++) { ~~^~~