Compilare: user.cpp: In function ‘bigint operator+(const bigint&, const bigint&)’: user.cpp:18:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < x.size(); i++) ^ user.cpp: In function ‘bigint operator-(const bigint&, const bigint&)’: user.cpp:34:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < x.size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:63:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < dp[n&1][k].size(); i++) ^