解題 32. Merge Two Sorted Lists

11 2 月, 2022 欣迪

You are given the heads of two sorted linked lists list1 and list2.

Merge the two lists in a one sorted list. The list should be made by splicing together the nodes of the first two lists.

Return the head of the merged linked list.

Example 1:

Input: list1 = [1,2,4], list2 = [1,3,4]
Output: [1,1,2,3,4,4]

Example 2:

Input: list1 = [], list2 = []
Output: []

Example 3:

Input: list1 = [], list2 = [0]
Output: [0]

Constraints:

The number of nodes in both lists is in the range [0, 50].
-100 <= Node.val <= 100
Both list1 and list2 are sorted in non-decreasing order.

對我來說，解 linked list 系列的圖目，就是畫圖, 畫圖, 畫圖。

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} list1
 * @param {ListNode} list2
 * @return {ListNode}
 */
var mergeTwoLists = function(list1, list2) {
    let newNode = new ListNode()
    let start = newNode
    while (list1 && list2) {
        if (list1.val <= list2.val) {
            newNode.next = new ListNode(list1.val, null)   
            list1 = list1.next
        } else {
            newNode.next = new ListNode(list2.val, null)
            list2 = list2.next
        }
        newNode = newNode.next
    }
    
    newNode.next = list1 ? list1 : list2
    
    return start.next
};

首先，我們要設置一個新的 node 當做開頭。