(链表) lintcode 219. Insert Node in Sorted Linked List

Posted 2021-10-20 weixu-liu

Description

 

Insert a node in a sorted linked list.

 

Example

Example 1:

Input: head = 1->4->6->8->null, val = 5
Output: 1->4->5->6->8->null

Example 2:

Input: head = 1->null, val = 2
Output: 1->2->null
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就是在一个有序的链表中插入一个数。
C++代码：
注意有表头，表中间和表尾三个情况

/**
 * Definition of singly-linked-list:
 * class ListNode {
 * public:
 *     int val;
 *     ListNode *next;
 *     ListNode(int val) {
 *        this->val = val;
 *        this->next = NULL;
 *     }
 * }
 */

class Solution {
public:
    /**
     * @param head: The head of linked list.
     * @param val: An integer.
     * @return: The head of new linked list.
     */
    ListNode * insertNode(ListNode * head, int val) {
        // write your code here
        ListNode *cur = new ListNode(val);
        ListNode *dummy = new ListNode(-1);
        dummy->next = head;
        if(!head) return cur;
        ListNode *p = dummy;
        while(p->next){
            if(p->next->val > val)
                break;
            else
                p = p->next;
        }
        cur->next = p->next;
        p->next = cur;
        return dummy->next;
    }
};