Compilare: user.cpp: In function ‘int main()’: user.cpp:34:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < arr.size(); i ++ ) { ^ user.cpp:42:63: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if( pos - i < 0 || pos + i > arr.size() - 1 || ^ user.cpp:46:64: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if( pos - i >= 0 && pos + i < arr.size() && arr[pos - i].first == arr[pos + i].first ) { ^