leetcode Remove Nth Node From End of List

原题链接：https://leetcode.com/problems/remove-nth-node-from-end-of-list/

Description

Given a linked list, remove the nth node from the end of list and return its head.

For example,

Given linked list: 1->2->3->4->5, and n = 2.

After removing the second node from the end, the linked list becomes 1->2->3->5.
Note:
Given n will always be valid.
Try to do this in one pass.

/** * 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) {        tot = 0;        if (!head) return head;        ListNode *p = head;        for (; p; p = p->next) tot++;        if (n > tot) return head;        p = head;        int cur = 1;        if (tot == n) {            head = head->next;            delete p;        } else {            while (p) {                if (cur++ == tot - n) break;                p = p->next;            }            ListNode *ret = p->next;            p->next = ret ? ret->next : NULL;            delete ret;        }        return head;    }private:    int tot;};