219. Insert Node in Sorted Linked List【Naive】

Insert a node in a sorted linked list.

Example

Given list = 1->4->6->8 and val = 5.

Return 1->4->5->6->8.

解法一：

/**
 * Definition of ListNode
 * 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) {
        ListNode * new_node = new ListNode(val);
        if (head == NULL) {
            return new_node;
        }
        
        ListNode * dummy = new ListNode(-1);
        dummy->next = head;
        head = dummy;
        
        while (head->next != NULL) {
            if (val > head->next->val) {
                head = head->next;
            } else {
                new_node->next = head->next;
                head->next = new_node;
                break;
            }
        }
        
        if (head->next == NULL) {
            head->next = new_node;
        }
        
        return dummy->next;
    }
};

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