技術標籤：LeetCode連結串列leetcodejava

題目

程式碼實現：

方法一：

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
 

class Solution {
    public ListNode removeElements(ListNode head, int val) {
        ListNode l0 = new ListNode(0);
        l0.next = head;

        ListNode pre = l0,cur = head;
        while(cur != null){
            if(cur.val == val){
                pre.next = cur.next;
            }else{
                pre =
 
 cur;
            }
            cur = cur.next;
        }
        return l0.next;
    }
}

結果：

方法二（遞迴）：

class Solution {
    public ListNode removeElements(ListNode head, int val) {
        if(head == null){
            return null;
        }
        head.next = removeElements(head.next,val);
        if
 
(head.val == val){
            return head.next;
        }else{
            return head;
        }
    }
}

結果：

方法三（頭節點特殊處理）：

class Solution {
    public ListNode removeElements(ListNode head, int val) {
        while(head != null && head.val == val){
            head = head.next;
        }
        if(head == null){
            return head;
        }
        ListNode previous = head;
        while(previous.next != null){
            if(previous.next.val == val){
                previous.next = previous.next.next;
            }else{
                previous = previous.next;
            }
        }
        return head;
    }
}

結果：