链表

package struct;

/**
 * Created by moi on 2017/10/18.
 */
public class LinkList {
    /**
     * Definition for singly-linked list.
     */
    public class ListNode {
        int val;
        ListNode next;

        ListNode(int x) {
            val = x;
        }
    }


    /**
     * 移除链表相同值
     * @param head a ListNode
     * @param val  an integer
     * @return a ListNode
     */
    public ListNode removeElements(ListNode head, int val) {
        if (head == null) {
            return null;
        }
        if (head.next == null) {
            if (head.val == val) {
                return null;
            } else {
                return head;
            }
        }
        ListNode current = head;
        ListNode pre = null;
        boolean flag = false;
        while (current.next != null) {
            if (current.val == val) {
                if (pre != null) {
                    pre.next = current.next;
                }
                current = current.next;
            } else {
                pre = current;
                if (flag == false) {
                    head = current;
                    flag = true;
                }
                current = current.next;
            }
        }
        if (pre == null) {
            return null;
        }
        if (current.next == null) {
            if (current.val == val) {
                pre.next = null;
            }
        }
        return head;

    }
    
}