Linked list (5)----Find the penultimate node of the linked list

1, linked list definition

typedef struct LISTELEMENT_T_ {    void *data;    struct Listelement_t_ *next;} listelement_t;typedef struct list_t_{    int size;    int capacity;    listelement_t *head;    listelement_t *tail;} list_t;

2. Find the K node data of the linked list

Set the speed pointer, the fast pointer ahead of the slow pointer K-1 nodes, and then the speed pointer and then traverse the linked list, when the fast pointer over the end of the list, the slow pointer is the bottom of the K node.

void  *searchrkthnode (list_t *list, unsigned int k) {    if (List = = NULL | | list->head = NULL | | k = = 0)//k is an unsigned number , so it is necessary to determine whether it is 0        return NULL;    listelement_t *pfast = list->head;    while (K > 1 && pfast! = NULL) {        --k;        Pfast = pfast->next;    }    K>1 indicates that the number of nodes is less than K, pfast=null indicates that the list is k-1 node    if (k > 1 | | pfast = = NULL)        return null;    listelement_t *pslow = list->head;    while (pfast->next! = NULL) {        pfast = pfast->next;        Pslow = pslow->next;    }    return pslow->data;}

Linked list (5)----Find the penultimate node of the linked list