C program Getchar mistake

Today I am helping my tutor-student debug his program which is a 2048 game.

Here is program

And I get the result

The result show two loops , char and ‘Enter’ as an input.Getchar or scanf where the input type is char , there is some problem here. The reason is it also take line Feed(LF) when you press enter . The line Feed(LF) still in the input buffer .

Method

We can clean the input buffer

I add input=getchar(); in line47

here getchar get the line Feed

Result