(LeetCode 21)Merge Two Sorted Lists
2015-04-27 21:16
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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.
2、递归思想(对于为改变链表结构的题目,一般也可以采用递归的方法)
题目要求:
合并两个有序链表注意:
不能开辟新的结点空间解题思路:
1、归并排序,创建一个新的头结点,从头到尾分别遍历两个链表,并依次比较其大小关系,每次将头指针指向小的那个。2、递归思想(对于为改变链表结构的题目,一般也可以采用递归的方法)
代码:
/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ // Merge combination method class Solution { public: ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) { ListNode head(0); ListNode *lst; lst=&head; while(l1 && l2){ if(l1->val<=l2->val){ lst->next=l1; l1=l1->next; } else{ lst->next=l2; l2=l2->next; } lst=lst->next; } if(l1) lst->next=l1; if(l2) lst->next=l2; return head.next; } }; // Recursive method 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(l2->next, l1); return l2; } }
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