LeetCode 筆記 - 2. Add Two Numbers

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題目在此 2. Add Two Numbers

給你兩個 Linked list，裏面各自 反序 存放一個數字
取出來相加之後，再依照 反序 的規則放進 Linked list

解題思維

在演算法上沒什麼特別，就是照著規則實作即可

Time complexity: O(n)

程式碼

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# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    
    
    def get_int(self, l):
        temp = ''
        
        while True:
            temp = f'{l.val}{temp}'
            
            if l.next is None:
                break
            
            l = l.next
        
        return int(temp)
    
    def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
        
        value = self.get_int(l1) + self.get_int(l2)
        result = [int(x) for x in reversed(str(value))]
        
        root = None
        last_node = None
        for x in result:
            node = ListNode(x)
            
            if root is None:
                root = node
            if last_node is not None:
                last_node.next = node
            last_node = node
        
        return root

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