移除链表中的倒数第N个数

1. LeetCode 19. Remove Nth Node From End of List

2. 描述：

给定一个链表，移除其从末尾数第n个节点

3. 示例：

输入： 1 -> 2 -> 3 -> 4 -> 5，n = 2 输出： 1 -> 2 -> 3 -> 5

4. 解决方案：

ListNode* RemoveNthFromEnd(ListNode* head, int n){
    if(head == nullptr|| n == 0){
        return head;
    }
    ListNode* pre_head = new ListNode(0);
    pre_head->next = head;
    ListNode* cur = pre_head;
    for(int i = 0; i < n + 1;i++){
        cur = cur->next;
    }
    ListNode* pre = pre_head;
    while(cur != nullptr){
        cur = cur->next;
        pre = pre->next;
    }
    ListNode* deleted_node = pre->next;
    pre->next = pre->next->next;
    delete deleted_node;
    head = pre_head->next;
    delete pre_head;
    return pre_head->next;
}