leetcode -- Merge Two Sorted Lists

上帝和每个人开的玩笑都不一样

[问题描述]

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

[解题思路]

添加一个新的头指针就可以了，合并链表相对简单

ListNode *Solution::mergeTwoLists(ListNode *l1, ListNode *l2)
{
    ListNode *ans = new ListNode(0);
    ListNode *ans1 = ans;
    while(l1 != NULL || l2 != NULL){
        if (l1 == NULL){
            ans->next = l2;
            break;
        }
        else if (l2 == NULL){
            ans->next = l1;
            break;
        }
        else{
            if (l1->val < l2->val){
                ans->next = l1;
                l1 = l1->next;
            }
            else{
                ans->next = l2;
                l2 = l2->next;
            }
            ans = ans->next;
        }
    }
    return ans1->next;
}