leetcode解题: Remove Linked List Elements (203)

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Remove all elements from a linked list of integers that have value val.

Example
Given: 1 –> 2 –> 6 –> 3 –> 4 –> 5 –> 6, val = 6
Return: 1 –> 2 –> 3 –> 4 –> 5

解法1： O(N) One Pass

要注意的是因为可能头指针会被删除或者整条list会被删，要用dummy node。
C++

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* removeElements(ListNode* head, int val) {
        ListNode* dummy = new ListNode(0);
        dummy->next = head;
        head = dummy;
        while (head->next) {
            if (head->next->val == val) {
                ListNode* temp = head->next;
                head->next = head->next->next;
                delete temp;
            } else {
                head = head->next;
            }
        }
        ListNode* res = dummy->next;
        delete dummy;
        return res;
    }
};

Java

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