题解 | 合并两个排序的链表

/**
 * struct ListNode {
 *  int val;
 *  struct ListNode *next;
 *  ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param pHead1 ListNode类
     * @param pHead2 ListNode类
     * @return ListNode类
     */
    ListNode* Merge(ListNode* pHead1, ListNode* pHead2) {
        // write code here
        ListNode* dummy = new ListNode(-1);
        ListNode* p = dummy;
        while (pHead1 || pHead2) {
            if (pHead1 == nullptr) {
                p->next = pHead2;
                p = p->next;
                break;
            }
            if (pHead2 == nullptr) {
                p->next = pHead1;
                p = p->next;
                break;
            }
            if (pHead1->val <= pHead2->val) {
                p->next = pHead1;
                p = p->next;
                pHead1 = pHead1->next;
            } else {
                p->next = pHead2;
                p = p->next;
                pHead2 = pHead2->next;
            }
        }
        return dummy->next;
    }
};