# 203 Remove Linked List Elements

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

Example:

Input:  1->2->6->3->4->5->6, val = 6
Output: 1->2->3->4->5

題目解析:

如上述範例，給一個linked list 及一個int val，若lined list裡有與val相同的值就刪掉。

實際上linked list並沒有刪掉，只是node的next不要指向val node即可。改指向下一個node即可

程式碼:

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode removeElements(ListNode head, int val) {
        if(head == null){
            return head;
        }
        ListNode slow = null;
        ListNode fast = head;
        // ListNode temp = null;
        while(fast != null){
            // if(fast.next != null){
            //     System.out.println("fast.val  = "+ fast.val + " , fast.next = "  + fast.next + " , fast.next.val = "  + fast.next.val);
            // }else{
            //     System.out.println("fast.val  = "+ fast.val + " , fast.next = "  + fast.next );
            // }
            if(fast.val == val){
                if(slow != null){
                    slow.next = fast.next;
                }else{
                    head = fast.next;
                }   
            }else{
                slow = fast;
            }
            fast = fast.next;
        }
        // //print 
        // temp = head;
        // while(temp !=  null){
        //     System.out.println("t  = "+ temp.val );
        //     temp = temp.next;
        // }
        return head;
    }
}