Eric 的小站

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输入：head = [1,2,3,4,5], n = 2
2
输出：[1,2,3,5]

1
输入：head = [1], n = 1
2
输出：[]

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/**
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 * Definition for singly-linked list.
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 * struct ListNode {
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 *     int val;
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 *     ListNode *next;
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 *     ListNode() : val(0), next(nullptr) {}
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 *     ListNode(int x) : val(x), next(nullptr) {}
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 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
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 * };
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 */
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class Solution {
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public:
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    ListNode* removeNthFromEnd(ListNode* head, int n) {
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        ListNode* result = new ListNode();
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        ListNode *p = head, *q = result;
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        int len = 0, count = 0;
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        while (p) {
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            len++;
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            p = p->next;
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        }
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        p = head;
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        while (p) {
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            count++;
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            if (count == (len - n + 1))
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                break;
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            q->next = p;
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            p = p->next;
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            q = q->next;
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        }
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        p = p->next;
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        q->next = p;
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        return result->next;
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    }
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};