2 Add Two Numbers

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2 Add Two Numbers

2. Add Two Numbers​
1. Question
You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.
Example
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Input:(2 -> 4 -> 3) + (5 -> 6 -> 4)
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​
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Output:7 -> 0 -> 8
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​
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Explanation: 342 + 465 = 807.
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2. Implementation
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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(int x) { val = x; }
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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 p1 = l1, p2 = l2;
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        ListNode dummy = new ListNode(0);
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        ListNode curNode = dummy;
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        int sum = 0;
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​
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        while (p1 != null || p2 != null) {
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            if (p1 != null) {
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                sum += p1.val;
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                p1 = p1.next;
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            }
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​
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            if (p2 != null) {
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                sum += p2.val;
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                p2 = p2.next;
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            }
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​
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            curNode.next = new ListNode(sum % 10);
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            curNode = curNode.next;
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            sum /= 10;
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        }
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​
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        if (sum != 0) {
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            curNode.next = new ListNode(sum);
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        }
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        return dummy.next;
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    }
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}
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3. Time & Space Complexity
时间复杂度O(m + n), m为第一个list的长度，n为第二个list的长度， 空间复杂度O(1)

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Contents

2. Add Two Numbers

1. Question

2. Implementation

3. Time & Space Complexity

2. Add Two Numbers​

1. Question

2. Implementation

3. Time & Space Complexity

2. Add Two Numbers