Compilare: user.cpp: In function ‘BigInt operator+(BigInt, BigInt)’: user.cpp:53:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < max(A.size(), B.size()); i++) { ^ user.cpp:54:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i < A.size()) { ^ user.cpp:57:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i < B.size()) { ^ user.cpp: In function ‘BigInt operator-(BigInt, BigInt)’: user.cpp:79:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < A.size(); i++) { ^ user.cpp: In function ‘BigInt operator*(BigInt, BigInt)’: user.cpp:100:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < A.size(); i++) { ^ user.cpp:102:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j < B.size() || carry > 0; j++) { ^ user.cpp:103:57: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] s = Ans[i + j] + carry + A[i] * (j < B.size() ? B[j] : 0); ^ user.cpp: In function ‘BigInt operator<<(std::ofstream&, BigInt)’: user.cpp:120:1: warning: no return statement in function returning non-void [-Wreturn-type] } ^