题解 | 合并两个排序的链表

仿归并排序就完事了

/**
 * 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* p = NULL;
        ListNode* head = NULL;
        // 分别指向两个链表
        ListNode* p1 = pHead1;
        ListNode* p2 = pHead2;
        if (p1 == NULL) {
            return pHead2;
        } else if (p2 == NULL) {
            return pHead1;
        }

        while(p1 != NULL && p2 != NULL) {
            if (p1->val < p2->val) {
                if (p == NULL) {
                    head = p1;
                    p = p1;
                    p1 = p1->next;
                    p->next = NULL;
                } else {
                    p->next= p1;
                    p1 = p1->next;
                    p = p->next;
                    p->next = NULL;
                }
            } else {
                if (p == NULL) {
                    head = p2;
                    p = p2;
                    p2 = p2->next;
                    p->next = NULL;
                } else {
                    p->next = p2;
                    p2 = p2->next;
                    p = p->next;
                    p->next = NULL;
                }
            }
        }

        if(p1 != NULL) {
            p->next = p1;
        } else if (p2 != NULL) {
            p->next = p2;
        }

        return head;
    }
};