LeetCode Merge Two Sorted Lists

最新推荐文章于 2025-04-27 14:03:08 发布

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本文介绍了一种合并两个已排序的单链表的方法，并通过拼接节点的方式返回一个新的排序链表。该算法首先检查输入链表是否为空，然后比较两链表的头节点值并进行连接，重复此过程直至遍历完所有节点。

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题目：

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.

/**
 * 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 && l2== NULL)
    		return NULL;
    	else if(l1 != NULL && l2 == NULL)
    		return l1;
    	else if(l1 == NULL && l2 != NULL)
    		return l2;   	
    	ListNode *head, *curr, *p1 = l1, *p2 = l2;
    	if(p1->val <= p2->val) {
    		head = p1;
    		p1 = p1->next;	
    	}
		else {
			head = p2;
			p2 = p2->next;
		} 
		curr = head;
		while(p1 != NULL && p2 != NULL) {
			if(p1->val <= p2->val) {
				curr->next = p1;
				p1 = p1->next;
			}
			else {
				curr->next = p2;
				p2 = p2->next;
			}
			curr = curr->next;
		}  
		while(p1 != NULL) {
			curr->next = p1;
			p1 = p1->next;
			curr = curr->next; 
		}
		
		while(p2 != NULL) {
			curr->next = p2;
			p2 = p2->next;
			curr = curr->next;
		}
		return head;
    }
};