Why is onlineGDB not giving the same result as another compiler?

onlinegdb OnlineGDB is a web-based IDE that offers an intuitive interface for writing code in various programming languages such as C, C++, Java, Python,

OnlineGDB is online IDE with C++ compiler Quick and easy way to compiler c++ program online It supports g++ compiler for c++  onlinegdb The OnlineGDB compiler supports over twenty popular programming languages including C++, Java, and Python To select C++, go to the “Language” pull down menu on