leetcode-21.Merge Two Sorted Lists 合併兩個有序連結串列
阿新 • • 發佈:2018-12-22
題目:
Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists. Example: Input: 1->2->4, 1->3->4 Output: 1->1->2->3->4->4 |
將兩個有序連結串列合併為一個新的有序連結串列並返回。新連結串列是通過拼接給定的兩個連結串列的所有節點組成的。 示例: 輸入:1->2->4, 1->3->4 輸出:1->1->2->3->4->4 |
思路:不要生成新節點,直接返回,利用遞迴思路。
/** * 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) { if(l1==NULL) return l2; if(l2==NULL) return l1; if(l1->val < l2->val) { l1->next = mergeTwoLists(l1->next,l2); return l1; } else { l2->next = mergeTwoLists(l1,l2->next); return l2; } } };