题解 | #合并两个排序的链表#

/**
 * public class ListNode {
 *   public var val: Int
 *   public var next: ListNode?
 *   public init(_ val: Int = 0, _ next: ListNode? = nil) {
 *     self.val = val
 *     self.next = next
 *   }
 * }
 */
public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param pHead1 ListNode类 
     * @param pHead2 ListNode类 
     * @return ListNode类
     */
    func Merge ( _ pHead1: ListNode?,  _ pHead2: ListNode?) -> ListNode? {
// write code here
        if pHead1 == nil {
            return pHead2
        }
        if pHead2 == nil {
            return pHead1
        }

        var node1 = pHead1
        var node2 = pHead2

        var res = ListNode()
        var node = res
        while node1 != nil && node2 != nil {
            if node1!.val < node2!.val {
                node.next = node1
                node1 = node1!.next
            } else {
                node.next = node2
                node2 = node2!.next
            }
            if let next = node.next {
                node = next
            }
        }
        if node1 == nil {
            node.next = node2
        }
        if node2 == nil {
            node.next = node1
        }
        return res.next
    }
}