leetcode 19

指针方面的问题

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
            ListNode *The_nth_node,*next,*header_first;
            int count=1;
           // The_nth_node=(struct ListNode *)malloc(sizeof(ListNode));
           // The_nth_node=(struct ListNode *)malloc(sizeof(ListNode));
            header_first=head;
            The_nth_node=head;
            //next=(struct ListNode *)malloc(sizeof(ListNode));
            while(head->next!=NULL&&count<=n) {
                count++;
                head=head->next;
            }
            if(count==n) {
                return The_nth_node->next;
            }
            while(head->next!=NULL) {
                head=head->next;
                The_nth_node=The_nth_node->next;
            }
            next=The_nth_node->next;
            The_nth_node->next=next->next;
          // free(next);
            return header_first;
    }
};