21. Merge Two Sorted Lists

21. Merge Two Sorted Lists

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.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var mergeTwoLists = function(l1, l2) {
    
    //这题其实是归并排序的子问题
    var newList = new ListNode(0);
    var cur = newList;
    var newNode =null;
    
    
    while(l1&&l2){
        if(l1.val < l2.val){
           newNode = new ListNode(l1.val);
        
            cur.next =  newNode;
            cur = cur.next;
            
           l1 = l1.next;
        
        }else{
            
            newNode = new ListNode(l2.val);
            cur.next =  newNode;
            cur = cur.next;          
            l2 = l2.next;
        }
    }
    
    while(l2){
         newNode = new ListNode(l2.val);
            cur.next =  newNode;
            cur = cur.next;          
            l2 = l2.next;
    }
    
    while(l1){
         newNode = new ListNode(l1.val);
        
            cur.next =  newNode;
            cur = cur.next;
            
           l1 = l1.next;
    }
    
    
    return newList.next;
    
};