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

/**
 * 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;
    }
};