合併兩個有序鏈表（C++）

簡述

將兩個有序的鏈表合併，並返回

輸入：1->2->4, 1->3->4
輸出：1->1->2->3->4->4

代碼

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
        ListNode *head=NULL, *cur=NULL;
        int val;
        while (l1 || l2) {
            if (l1 != NULL && l2 != NULL) { 
                if (l1 -> val < l2 -> val){
                    val = l1->val;
                    l1 = l1 -> next;
                } else {
                    val = l2->val;
                    l2 = l2 -> next;
                }
            } else  if (l1 != NULL) {
                val = l1 -> val;
                l1 = l1 -> next;
            } else if (l2 != NULL) {
                val = l2 -> val;
                l2 = l2 -> next;
            }
            if (head == NULL) {
                head = new ListNode(val);
                cur = head;
            } else {
                cur->next = new ListNode(val);
                cur = cur->next;
            }
        }
        return head;
    }
};