如何在递归中找到C中元素的索引

Question

i have this, it checks if element is in list or not, but how get the index of element ?

// function that check if element is in list
int checklist(struct list *my_list, int n) {
  while (my_list != NULL) {
    if(my_list->info == n) return 1;
    my_list = my_list->next;
  }
  return 0;
}

Answer 1

Use additional variable to remember the current index:

int checklist (struct list *my_list,int n) {
int i=0;
while (my_list != NULL) {
 if(my_list->info == n) return i;
 my_list = my_list->next;
 i++;
 }
return -1; 
}

or

int checklist (struct list *my_list,int n) {
int i;
for (i=0;my_list != NULL; i++, my_list = my_list->next) 
 if(my_list->info == n) return i;
return -1; 
}

By the way your code has nothing to do with recursion, i think its called linked list.

Answer 2

Use an additional argument to the function which carries the index you're currently looking at. Though you need a way to return it: return -1 if the list is exhausted and the index of the first found item otherwise.

PS I don't see any recursion here.