LintCode - Merge Two Sorted List

LintCode - Merge Two Sorted Lists

• LintCode - Merge Two Sorted Lists

Web Link

http://www.lintcode.com/en/problem/merge-two-sorted-lists/

Description

Merge two sorted (ascending) linked lists and return it as a new sorted list. The new sorted list should be made by splicing together the nodes of the two lists and sorted in ascending order.
Example
Given 1->3->8->11->15->null, 2->null , return 1->2->3->8->11->15->null.

Code - C++

/**
 * Definition of ListNode
 * class ListNode {
 * public:
 *     int val;
 *     ListNode *next;
 *     ListNode(int val) {
 *         this->val = val;
 *         this->next = NULL;
 *     }
 * }
 */
class Solution {
public:
    /**
     * @param ListNode l1 is the head of the linked list
     * @param ListNode l2 is the head of the linked list
     * @return: ListNode head of linked list
     */
    ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) {
        // write your code here
        if (l1 == NULL) {
            return l2;
        }
        if (l2 == NULL) {
            return l1;
        }
        ListNode* head = l1->val < l2->val ? l1:l2;
        ListNode* temp = new ListNode(0);
        while (l1 != NULL && l2 != NULL) {
            if (l1->val < l2->val) {
                temp->next = l1;
                temp = l1;
                l1 = l1->next;
            } else {
                temp->next = l2;
                temp = l2;
                l2 = l2->next;
            }
        }
        if (l1 == NULL) {
            temp->next = l2;
        }
        if (l2 == NULL) {
            temp->next = l1;
        }
        return head;
    }
};

Tips

None