LeetCode(52)-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

思路：

题意：有序列表里面去掉给定的元素遍历发现相同的，就去掉，prev.next ！= null，发现了prev.next = prev.next.next 考虑头部满足条件的情况，那就一直删除下去 -

代码：

/**
 * definition for singly-linked list.
 * public class listnode {
 *     int val;
 *     listnode next;
 *     listnode(int x) { val = x; }
 * }
 */
public class solution {
    public listnode removeelements(listnode head, int val) {
        if(head == null){
            return null;
        }
        while(head.val == val){
            head = head.next;
            if(head == null){
                return null;
            }
        }
        listnode prev = head;
        while(prev.next != null){
            while(prev.next.val == val){
                prev.next = prev.next.next;
                if(prev.next == null){
                return head;
            }
            }
            prev = prev.next;
        }
        return head;
    }
}