[Algorithm] 32 week(9.05 ~ 9.11) 3/3

21. Merge Two Sorted Lists

var mergeTwoLists = function(list1, list2) {
    let mergedlist = new ListNode
    let change = mergedlist;
    
    
    while(list1 !== null && list2 !== null){
        
        if(list1.val <= list2.val){
            change.next = list1;
            list1 = list1.next;
        }else{
            change.next = list2;
            list2 = list2.next;
        }
        
        change = change.next;
        
        
    }
    
    if(list1 !== null){
        change.next = list1;
    }
    if(list2 !== null){
        change.next = list2;
    }
    
    return mergedlist.next;    
};