【LeetCode】【esay】【13】合併兩個有序列表

將兩個升序鏈表合併爲一個新的升序鏈表並返回。新鏈表是通過拼接給定的兩個鏈表的所有節點組成的。 

示例：

輸入：1->2->4, 1->3->4
輸出：1->1->2->3->4->4

// @lc code=start
/**
 * 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) {

    let comm = new ListNode();
    let dummy = comm;

    while(l1!==null&&l2!==null){

        if(l1.val < l2.val){

            comm.next = l1;
            l1 = l1.next;
            comm = comm.next;
        }
        else if(l1.val == l2.val){
            comm.next = l1;
            l1 = l1.next;
            comm = comm.next;
            comm.next = l2;
            l2 = l2.next;
            comm = comm.next;
        }
        else{
            comm.next = l2;
            l2 = l2.next;
            comm = comm.next;
        }
        // comm = comm.next;
    }

    if(l1!==null){
        comm.next = l1;
    }

    if(l2!==null){
        comm.next = l2;
    }
    return dummy.next;

};