203. Remove Linked List Elements

题目

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

Credits:

Special thanks to @mithmatt for adding this problem and creating all test cases.

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思路

遍历链表删除对应节点，注意删除首节点，尾节点，最后删除后为NULL的场景

代码

/**
* 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) {
if(head == NULL)
{
return NULL;
}
ListNode* tempHead = new ListNode(0);
tempHead->next = head;
ListNode* tempNode = tempHead;
ListNode* freeNode;

while(tempNode->next)
{
if(tempNode->next->val == val)
{
freeNode = tempNode->next;
tempNode->next = freeNode->next;
free(freeNode);
continue;
}
tempNode = tempNode->next;
}

tempNode = tempHead->next;
free(tempHead);
return tempNode;
}
};