两个数相加

给出两个 非空 的链表用来表示两个非负的整数。其中，它们各自的位数是按照 逆序 的方式存储的，并且它们的每个节点只能存储 一位 数字。

如果，我们将这两个数相加起来，则会返回一个新的链表来表示它们的和。

您可以假设除了数字 0 之外，这两个数都不会以 0 开头。

输入：(2 -> 4 -> 3) + (5 -> 6 -> 4)
输出：7 -> 0 -> 8
原因：342 + 465 = 807

package com.leetcode.part1;

/**
 * @author ：shix
 * @date ：Created in 2020/1/26 14:09
 * @description：两数相加
 * @modified By：
 */
public class AddTwoNumbers {


    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode head = null;//返回结果
        ListNode previousNode = null;//存储上一个节点
        boolean flag = false;//是否进位
        ListNode p1 = l1;
        ListNode p2 = l2;
        while (p1 != null && p2 != null) {
            int temp = p1.val + p2.val + (flag ? 1 : 0);
            ListNode node;
            if (temp >= 10) {
                node = new ListNode(temp - 10);
                flag = true;
            } else {
                node = new ListNode(temp);
                flag = false;
            }
            if (head == null && previousNode == null) {
                head = node;
                previousNode = node;
            } else {
                previousNode.next = node;
            }
            node.next = null;
            previousNode = node;

            p1 = p1.next;
            p2 = p2.next;
        }
        while (p1 != null) {
            int temp = p1.val + (flag ? 1 : 0);
            ListNode node;
            if (temp >= 10) {
                node = new ListNode(temp - 10);
                flag = true;
            } else {
                node = new ListNode(temp);
                flag = false;
            }
            node.next = null;
            previousNode.next = node;
            previousNode = node;
            p1 = p1.next;
        }
        while (p2 != null) {
            int temp = p2.val + (flag ? 1 : 0);
            ListNode node;
            if (temp >= 10) {
                node = new ListNode(temp - 10);
                flag = true;
            } else {
                node = new ListNode(temp);
                flag = false;
            }
            node.next = null;
            previousNode.next = node;
            previousNode = node;
            p2 = p2.next;
        }
        if (flag == true) {
            ListNode node = new ListNode(1);
            previousNode.next = node;
        }
        return head;
    }

    /**
     * 初始化ListNode
     *
     * @param num
     * @return
     */
    public ListNode initNode(int num) {
        int temp = num % 10;
        ListNode head = null;
        ListNode previousNode = null;
        while (temp != 0) {
            ListNode node = new ListNode(temp);
            node.next = null;
            if (head == null && previousNode == null) {
                head = node;
                previousNode = node;
            } else {
                previousNode.next = node;
            }
            num = num / 10;
            temp = num % 10;
            previousNode = node;
        }
        return head;
    }

    public static void main(String[] args) {
        AddTwoNumbers add = new AddTwoNumbers();
        //初始化两个链表
        ListNode l1 = add.initNode(342);
        ListNode l2 = add.initNode(465);
        //两数相加
        ListNode result = add.addTwoNumbers(l1, l2);
        // 打印结果
        add.printResult(result);
    }

    private void printResult(ListNode result) {
        //打印结果
        System.out.print("结果：");
        while (result != null) {
            System.out.print(result.val);
            if (result.next != null) {
                System.out.print("->");
            }
            result = result.next;
        }
        System.out.println("");
    }

    class ListNode {
        int val;
        ListNode next;

        ListNode(int x) {
            val = x;
        }
    }
}

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/add-two-numbers
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

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