21.merge-two-sorted-lists.cpp

/**
 * 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 = ListNode(0);
        ListNode* cur = &head;
        
        while (l1 && l2) {
            if (l1->val <= l2->val)
            {
                cur->next = l1;
                l1 = l1->next;
                cur = cur->next;
            }
            else if (l1->val > l2->val)
            {
                cur->next = l2;
                l2 = l2->next;
                cur = cur->next;
            }
        }
        
        if (l1)
        {
            cur->next = l1;
        }
        
        if (l2)
        {
            cur->next = l2;
        }
        
        return head.next;
    }
};