技術標籤：lankerenFrequency連結串列指標JavaByteDance

LeetCode： 21. 合併兩個有序連結串列

歸併排序 >> 一條連結串列 >> 時間複雜度 >> O(nlogn)

這裡合併兩條連結串列 >> 雙指標就行，誰小接誰

雙指標

/**
 * 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 mergeTwoLists(ListNode head, ListNode head2) {
        ListNode h1 = head, h2 = head2;
        if(h1 == null && h2 == null) return null;
        if(h1 == null) return h2;
        if(h2 == null) return h1;
        ListNode h = new ListNode();
        ListNode ans =
 
 h;
        while(h1 != null && h2 != null){
            if(h1.val < h2.val) {
                h.next = h1;
                h1 = h1.next;
            }
            else if(h1.val >= h2.val){
                h.next = h2; 
                h2 = h2.next;
            }
            h = h.next;
 

        }

        if(h1 != null){
            h.next = h1;
        }
        if(h2 != null){
            h.next = h2;
        }

        return ans.next;
    }
}