Merge Two Sorted Lists

最新推荐文章于 2024-01-12 14:30:52 发布

原创最新推荐文章于 2024-01-12 14:30:52 发布 · 477 阅读

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (!l1||!l2) {
            return NULL;
        }
        ListNode *head= NULL;
        ListNode *res= head;
        ListNode *prev= head;
        while (l1 && l2) {
            if (l1->val < l2->val) {
                res= l1;
                l1=l1->next;
                prev->next=res;
                prev=res;
            }else {
                res= l2;
                l2=l2->next;
                prev->next=res;
                prev=res;
            }
            
        }
        if (l1!=NULL) {
            res=l1;
        } else if (l2!=NULL) {
            res=l2;
        }
        return head;
    }
};

Recursion

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (l1==NULL) return l2;
        if (l2==NULL) return l1;
        ListNode* res=NULL;
        if (l1->val < l2->val) {
            res=l1;
            res->next=mergeTwoLists(l1->next, l2);
        }else {
            res=l2;
            res->next=mergeTwoLists(l1,l2->next);
        }
        return res;
    }
};