[Leetcode] 2번 - Add Two Numbers (Java, Kotlin)

2. Add Two Numbers (Medium)

 

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:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)

Output: 7 -> 0 -> 8

Explanation: 342 + 465 = 807.

 

 

Java Solution

class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode answer = new ListNode(l1.val);
        ListNode temp = answer;

        while(l1.next != null) {
            temp.next = new ListNode(l1.next.val);
            l1 = l1.next;
            temp = temp.next;
        }
        
        int p = 0;
        temp = answer;
        while(l2 != null || p == 1) {
            int sum = l2 != null ? temp.val + l2.val : temp.val;
            p = sum >= 10 ? 1 : 0;
            temp.val = sum % 10;

            if(p == 1) {
                if(temp.next != null) {
                    temp.next.val += p;
                } else {
                    temp.next = new ListNode(p);
                }
            }
            l2 = l2 != null ? l2.next : null;
            temp.next = temp.next == null ? (l2 != null ? new ListNode(0) : null) : temp.next;
            temp = temp.next;
        }

        return answer;
    }
}

 

Kotlin Solution

/**
 * Example:
 * var li = ListNode(5)
 * var v = li.`val`
 * Definition for singly-linked list.
 * class ListNode(var `val`: Int) {
 *     var next: ListNode? = null
 * }
 */

class Solution {
    fun addTwoNumbers(l1: ListNode?, l2: ListNode?): ListNode? {
        var tmp1: ListNode? = l1
        var tmp2: ListNode? = l2
        var carry: Int = 0

        val ans = ListNode(-1)
        var tmpAns = ans

        while(tmp1 != null || tmp2 != null || carry > 0) {
            var cal = 0
            tmp1?.let {
                cal += it.`val`
                tmp1 = it.next
            }
            tmp2?.let {
                cal += it.`val`
                tmp2 = it.next
            }
            
            cal += carry
            if(cal >= 10) {
                carry = 1
                cal %= 10
            } else {
                carry = 0
            }

            tmpAns.next = ListNode(cal)
            tmpAns = tmpAns.next!!
        }


        return ans.next
    }
}

 

이 외에도 다양한 문제들의 해답 코드를 깃헙 저장소에서 확인할 수 있습니다. (Java, Kotlin)

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