merge 2 lists.py

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    # @param two ListNodes
    # @return a ListNode
    def mergeTwoLists(self, l1, l2):
        if not l1:
            return l2
        if not l2:
            return l1
            
        if l1.val > l2.val:
            newHead = l2
            l2 = l2.next
        else:
            newHead = l1
            l1 = l1.next
        p = newHead
        while l1 or l2:
            if l1 and l2:
                if l1.val > l2.val:
                    p.next = l2
                    l2 = l2.next
                else:
                    p.next = l1
                    l1 = l1.next
            elif l1:
                p.next = l1;
                break;
            else:
                p.next = l2
                break;
            p = p.next
                
        return newHead