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
        if (pHead1 == nullptr) return pHead2;
        if (pHead2 == nullptr) return pHead1;

        ListNode *dummy = new ListNode(-1);
        ListNode *cur = dummy;

        while (pHead1!=nullptr && pHead2!=nullptr) {
            if (pHead1->val < pHead2->val) {
                cur->next = pHead1;

                pHead1 = pHead1->next;
                cur = cur->next;
                
            } else if (pHead1->val > pHead2->val) {
                cur->next = pHead2;

                pHead2 = pHead2->next;
                cur = cur->next;
            } else {
                cur->next = pHead1;
                pHead1 = pHead1->next;
                cur = cur->next;

                cur->next = pHead2;
                pHead2 = pHead2->next;
                cur = cur->next;
            }
        }
        // link tail
        if (pHead1!=nullptr) {
            cur->next = pHead1;
        }
        if (pHead2!=nullptr) {
            cur->next = pHead2;

        }
        return  dummy->next;
    }
};

这道题和归并排序 或者 两个非递减序列合并的思路是一样的，