LeetCode:2. 两数相加

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/**
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 * Definition for singly-linked list.
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 * public class ListNode {
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 *     int val;
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 *     ListNode next;
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 *     ListNode() {}
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 *     ListNode(int val) { this.val = val; }
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 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
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 * }
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 */
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class Solution {
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    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
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        ListNode p = new ListNode(0);
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        ListNode cur = p;
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        int pp = 0;
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        while (l1 != null || l2 != null || pp != 0) {
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            int s1 = l1 != null ? l1.val : 0;
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            int s2 = l2 != null ? l2.val : 0;
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            int add = s1 + s2 + pp;
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            pp = add >= 10 ? 1 : 0;
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            add = add >= 10 ? add - 10 : add;
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            cur.next = new ListNode(add);
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            cur = cur.next;
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            if (l1 != null) {
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                l1 = l1.next;
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            }
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            if (l2 != null) {
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                l2 = l2.next;
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            }
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        }
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        return p.next;
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    }
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}