/in/foo.c:24:26: error: expected ';', ',' or ')' before '&' token
 void Insert(struct Node* &head, int x)
                          ^
/in/foo.c: In function 'main':
/in/foo.c:52:9: warning: implicit declaration of function 'Insert' [-Wimplicit-function-declaration]
         Insert(head, k);
         ^~~~~~