---
title: 'LeetCode 203. Remove Linked List Elements'
disqus: hackmd
---

# LeetCode 203. Remove Linked List Elements

## Description

Given the head of a linked list and an integer val, remove all the nodes of the linked list that has Node.val == val, and return the new head.

## Example

Input: head = [1,2,6,3,4,5,6], val = 6
Output: [1,2,3,4,5]
## Constraints

The number of nodes in the list is in the range [0, 10^4^].
1 <= Node.val <= 50
0 <= val <= 50

## Answer

此題先抓出第一非目標點當頭，再一一往下檢查誰要刪除。注意不要檢查完一次就馬上往下推，而是確認下一點不為目標才往下走，所以為防止替換完的點仍為目標點，所以我們換完之後不馬上往下走，而是在做一次檢查，確保不是連續的目標點。

//0222_03_12
struct ListNode* removeElements(struct ListNode* head, int val){
    struct ListNode * opr = head, *del = NULL;
    while(opr != NULL && opr->val == val){
        del = opr;
        opr = opr->next;
        free(del);
    }
    head = opr;
    while(opr != NULL && opr->next != NULL){
        if(opr->next->val == val){
            del = opr->next;
            opr->next = del->next;
            free(del);
        }
        else{
            opr = opr->next;
        }
    }
    return head;
}

## Link
https://leetcode.com/problems/remove-linked-list-elements/
###### tags: `Leetcode`