题目浅析

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  • 简单地说，给两个链表代表数字，每个节点代表一位，求和，但是这次的链表头是大值位。

思路分享

代码解答（强烈建议自行解答后再看）

  • 参考题解
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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 addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
        l1_nums = []
        l2_nums = []
        while l1 or l2:
            cur = 0
            if l1:
                l1_nums.append(l1.val)
                l1 = l1.next
            if l2:
                l2_nums.append(l2.val)
                l2 = l2.next


        nums = [0] * max(len(l1_nums), len(l2_nums))
        for i in range(len(nums)):
            if i < len(l1_nums):
                nums[-i-1] += l1_nums[-i-1]
            if i < len(l2_nums):
                nums[-i-1] += l2_nums[-i-1]
            
        pre = None
        last_add = 0
        for num in nums[::-1]:
            if last_add > 0:
                num += 1
                last_add = 0

            if num >= 10:
                last_add = 1
                num -= 10

            pre = ListNode(num, pre)
        
        if last_add > 0:
            pre = ListNode(1, pre)
        
        return pre