LintCode-174.删除链表中倒数第n个节点

删除链表中倒数第n个节点

code

/**
* Definition of ListNode
* class ListNode {
* public:
*     int val;
*     ListNode *next;
*     ListNode(int val) {
*         this->val = val;
*         this->next = NULL;
*     }
* }
*/
class Solution {
public:
/**
* @param head: The first node of linked list.
* @param n: An integer.
* @return: The head of linked list.
*/
ListNode *removeNthFromEnd(ListNode *head, int n) {
// write your code here
if(n > 0) {
ListNode *pBegin=head, *pEnd=head;
while(n-- && pEnd!=NULL) {
pEnd = pEnd->next;
}
//  n<链表长度
if(n == -1 && pEnd!=NULL) {
while(pEnd->next != NULL) {
pBegin = pBegin->next;
pEnd = pEnd->next;
}
pBegin->next = pBegin->next->next;
return head;
}
//  n>链表长度
else if(n > -1 && pEnd!=NULL) {
return head;
}
//  n=链表长度
else {
return head->next;
}
}
}
};