Leetcode刷题笔记(c++)

class Solution {
public:
    ListNode* mergeTwoLists(ListNode* list1, ListNode* list2) {
        if(!list1)return list2;
        if(!list2)return list1;
        if(list1->val>=list2->val){
            list2->next=mergeTwoLists(list1,list2->next);
            return list2;
        }else{
            list1->next=mergeTwoLists(list1->next,list2);
            return list1;            
        }    
    }
};

class Solution {
public:
    ListNode* mergeTwoLists(ListNode* list1, ListNode* list2) {
        if(!list1)return list2;
        if(!list2)return list1;
        auto list11=new ListNode();
        list11->next=list1;
        auto list1_pro=list11; 
        while(list1||list2){
            if(list1&&list2){
                if(list1->val>=list2->val){
                    list1_pro->next=list2;
                    list2=list2->next;
                    list1_pro=list1_pro->next;
                    list1_pro->next=list1;
                }else{
                    list1=list1->next;
                    list1_pro=list1_pro->next;
                }
            }else if(!list1&&list2){
                // cout<val<<" "<val;
                list1_pro->next=list2;
                break;
            }else if(list1&&!list2){
                break;
            }
        }
        return list11->next;        
    }
};