Compilare: user.c: In function ‘createStackElement’: user.c:18: warning: implicit declaration of function ‘malloc’ user.c:18: warning: incompatible implicit declaration of built-in function ‘malloc’ user.c: In function ‘solve’: user.c:28: warning: incompatible implicit declaration of built-in function ‘malloc’ user.c:46: warning: implicit declaration of function ‘free’ user.c:46: warning: incompatible implicit declaration of built-in function ‘free’ user.c:66: warning: incompatible implicit declaration of built-in function ‘free’ user.c:83: warning: incompatible implicit declaration of built-in function ‘free’ user.c: In function ‘main’: user.c:107: warning: incompatible implicit declaration of built-in function ‘malloc’ user.c:124: warning: incompatible implicit declaration of built-in function ‘free’ user.c:106: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result user.c:112: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result user.c:127: warning: control reaches end of non-void function