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Add Two Numbers

https://oj.leetcode.com/problems/add-two-numbers/

You are given two linked lists representing two non-negative numbers. 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.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

下面是一个不能处理超长数据的答案。

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { *         val = x; *         next = null; *     } * } */public class Solution {    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {        ListNode node = l1;        int l1Value = http://www.mamicode.com/0;        int count = 0;        while(node != null){            l1Value = l1Value + node.val * ((Double)Math.pow(10, count)).intValue();            count ++;            node = node.next;        }                node = l2;        int l2Value = http://www.mamicode.com/0;        count = 0;        while(node != null){            l2Value = l2Value + node.val * ((Double)Math.pow(10, count)).intValue();            count++;            node = node.next;        }                int sumValue = http://www.mamicode.com/l1Value + l2Value;                //int digits = (Math.floor((Double)(Math.log(sumValue) / Math.log(10) + 1)).intValue());         int digits = String.valueOf(sumValue).length();        if(sumValue < 10){            digits = 1;        }        ListNode[] listNodes = new ListNode[digits];                listNodes[0] = new ListNode(sumValue % 10);        sumValue = sumValue / 10;                for(int i = 1; i < digits; i++){            listNodes[i] = new ListNode(sumValue % 10);            listNodes[i - 1].next = listNodes[i];            sumValue = sumValue / 10;        }        return listNodes[0];    }}

 下面是一个AC的方法。技巧是,对于为null的node,全部置为0,再运算。

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { *         val = x; *         next = null; *     } * } */public class Solution {    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {        ListNode node1 = l1;        ListNode node2 = l2;        ListNode node_current = new ListNode(0);        ListNode node_next = node_current;        ListNode node_return = node_current;                while(node1 != null || node2 != null){            if(node1 == null){                node1 = new ListNode(0);            }            if(node2 == null){                node2 = new ListNode(0);            }            int sum = node1.val + node2.val + node_current.val;            node_current.val = (node1.val + node2.val + node_current.val) % 10;            if(sum > 9 || node1.next != null || node2.next !=null){                node_next = new ListNode(sum / 10);                node_current.next = node_next;            }            node_current = node_next;            if(node1 != null){                node1 = node1.next;            }            if(node2 != null){                node2 = node2.next;            }        }        return node_return;    }}

 

Add Two Numbers