#2 Add Two Numbers 兩數之和

just for the record, not the best solutions.

if you like to study together, my discord: Journey#9805

package com.journey;


public class AddTwoNumbers_兩數相加_002 {
    //solution
    public static ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode pre = new ListNode(0);
        ListNode cur = pre;
        int carry = 0;//進位

        while (l1 != null || l2 != null) {
            int x = l1 == null ? 0 : l1.val; //如果null就補0  
            int y = l2 == null ? 0 : l2.val; //如果null就補0  
            int sum = x + y + carry;

            carry = sum / 10;               //看是有要進位
            sum = sum % 10;                 //得出個位數
            cur.next = new ListNode(sum);   //cur.next  = 0.next = 指向個位數（sum）
            cur = cur.next;                 //個位數的next = 十位數

            if (l1 != null) {               //如果還有,指向下一位
                l1 = l1.next;
            }
            if (l2 != null) {               //如果還有,指向下一位
                l2 = l2.next;
            }
        }

        //退出循环
        if (carry == 1) {                   //最后如果有進位，新增node
            cur.next = new ListNode(carry);
        }
        return pre.next;
    }


    //test 
    public static void main(String[] args) {
        ListNode node1 = new ListNode(7, new ListNode(8, new ListNode(9)));
        ListNode node2 = new ListNode(2, new ListNode(3, new ListNode()));
        ListNode answer = addTwoNumbers(node1, node2);
        System.out.println(answer.val);
        System.out.println(answer.next.val);
        System.out.println(answer.next.next.val);
        System.out.println(answer.next.next.next.val);
    }
}


//constructor
class ListNode {
    int val;
    ListNode next;

    ListNode() {
    }

    ListNode(int val) {
        this.val = val;
    }

    ListNode(int val, ListNode next) {
        this.val = val;
        this.next = next;
    }

}

Add Two Numbers - LeetCode

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