LeetCode-19-Remove Nth Node From End of List(C语言实现)

/**

 * Definition for singly-linked list.

 * struct ListNode {

 *     int val;

 *     struct ListNode *next;

 * };

 */

struct ListNode* removeNthFromEnd(struct ListNode* head, int n) {

    int i;

    struct ListNode *p, *q, *tmp;

    p = head;

    q = head;

    for(i = 0; i < n; ++i)

        q = q -> next;

    if(q == NULL)

    {

        tmp = p;

        p = p -> next;

        free(tmp);

        return p;

    }

    while(q -> next != NULL)

    {

        p = p-> next;

        q = q -> next;

    }

    tmp = p -> next;

    p -> next = tmp -> next;

    free(tmp);

    return head;

}