报错unknown type name 'list';did you mean 'uint'

#include <stdio.h>

int round(list *head)
{
list *slow=head;
list *fast=head;
while(fast&&fast->next)
{
slow=slow->next;
fast=fast->next->next;
if(slow==fast)
{
return true;
break;
}
}
return false;

}