LeetCode 445. 两数相加 II(Add Two Numbers II)

445. 两数相加 II

445. Add Two Numbers II

题目描述

给定两个非空链表来代表两个非负整数。数字最高位位于链表开始位置。它们的每个节点只存储单个数字。将这两数相加会返回一个新的链表。

你可以假设除了数字 0 之外，这两个数字都不会以零开头。

进阶:

如果输入链表不能修改该如何处理？换句话说，你不能对列表中的节点进行翻转。

LeetCode445. Add Two Numbers II中等

示例:

输入: (7 -> 2 -> 4 -> 3) + (5 -> 6 -> 4)
输出: 7 -> 8 -> 0 -> 7

Java 实现

public class ListNode {

    int val;

    ListNode next;

    ListNode(int x) {

        val = x;

    }

    @Override

    public String toString() {

        return val + "->" + next;

    }

}

import java.util.Stack;

class Solution {

    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

        Stack<Integer> s1 = new Stack<Integer>();

        Stack<Integer> s2 = new Stack<Integer>();

        while (l1 != null) {

            s1.push(l1.val);

            l1 = l1.next;

        }

        while (l2 != null) {

            s2.push(l2.val);

            l2 = l2.next;

        }

        int sum = 0;

        ListNode list = new ListNode(0);

        while (!s1.empty() || !s2.empty()) {

            if (!s1.empty()) sum += s1.pop();

            if (!s2.empty()) sum += s2.pop();

            list.val = sum % 10;

            ListNode head = new ListNode(sum / 10);

            head.next = list;

            list = head;

            sum /= 10;

        }

        return list.val == 0 ? list.next : list;

    }

}

测试代码

import java.util.Stack;

class Solution {

    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

        Stack<Integer> s1 = new Stack<Integer>();

        Stack<Integer> s2 = new Stack<Integer>();

        while (l1 != null) {

            s1.push(l1.val);

            l1 = l1.next;

        }

        while (l2 != null) {

            s2.push(l2.val);

            l2 = l2.next;

        }

        int sum = 0;

        ListNode list = new ListNode(0);

        while (!s1.empty() || !s2.empty()) {

            if (!s1.empty()) sum += s1.pop();

            if (!s2.empty()) sum += s2.pop();

            list.val = sum % 10;

            ListNode head = new ListNode(sum / 10);

            head.next = list;

            list = head;

            sum /= 10;

            System.out.println(list);

        }

        return list.val == 0 ? list.next : list;

    }

    public static void main(String[] args) {

        ListNode t1 = new ListNode(7);

        ListNode t2 = new ListNode(2);

        ListNode t3 = new ListNode(4);

        ListNode t4 = new ListNode(3);

        t1.next = t2;

        t2.next = t3;

        t3.next = t4;

        ListNode p1 = new ListNode(5);

        ListNode p2 = new ListNode(6);

        ListNode p3 = new ListNode(4);

        p1.next = p2;

        p2.next = p3;

        System.out.println(new Solution().addTwoNumbers(t1, p1));

    }

}

测试结果

0->7->null
1->0->7->null
0->8->0->7->null
0->7->8->0->7->null
7->8->0->7->null

相似题目

2. 两数相加 Add Two Numbers

参考资料

https://leetcode.com/problems/add-two-numbers-ii/
https://leetcode-cn.com/problems/add-two-numbers-ii/

LeetCode 445. 两数相加 II(Add Two Numbers II)的相关教程结束。